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
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  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
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  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     Other,
  44     Uninit
  45   };
  46 
  47   enum Flags {
  48     None                = 0,
  49     TargetUninitialized = 1
  50   };
  51 protected:
  52   int _max_covered_regions;
  53   Name _kind;
  54 
  55 public:
  56 
  57   BarrierSet() { _kind = Uninit; }
  58   // To get around prohibition on RTTI.
  59   BarrierSet::Name kind() { return _kind; }
  60   virtual bool is_a(BarrierSet::Name bsn) = 0;
  61 
  62   // These operations indicate what kind of barriers the BarrierSet has.
  63   virtual bool has_read_ref_barrier() = 0;
  64   virtual bool has_read_prim_barrier() = 0;
  65   virtual bool has_write_ref_barrier() = 0;
  66   virtual bool has_write_ref_pre_barrier() = 0;
  67   virtual bool has_write_prim_barrier() = 0;
  68 
  69   // These functions indicate whether a particular access of the given
  70   // kinds requires a barrier.
  71   virtual bool read_ref_needs_barrier(void* field) = 0;
  72   virtual bool read_prim_needs_barrier(HeapWord* field, size_t bytes) = 0;
  73   virtual bool write_prim_needs_barrier(HeapWord* field, size_t bytes,
  74                                         juint val1, juint val2) = 0;
  75 
  76   // The first four operations provide a direct implementation of the
  77   // barrier set.  An interpreter loop, for example, could call these
  78   // directly, as appropriate.
  79 
  80   // Invoke the barrier, if any, necessary when reading the given ref field.
  81   virtual void read_ref_field(void* field) = 0;
  82 
  83   // Invoke the barrier, if any, necessary when reading the given primitive
  84   // "field" of "bytes" bytes in "obj".
  85   virtual void read_prim_field(HeapWord* field, size_t bytes) = 0;
  86 
  87   // Invoke the barrier, if any, necessary when writing "new_val" into the
  88   // ref field at "offset" in "obj".
  89   // (For efficiency reasons, this operation is specialized for certain
  90   // barrier types.  Semantically, it should be thought of as a call to the
  91   // virtual "_work" function below, which must implement the barrier.)
  92   // First the pre-write versions...
  93   template <class T> inline void write_ref_field_pre(T* field, oop new_val);
  94 private:
  95   // Keep this private so as to catch violations at build time.
  96   virtual void write_ref_field_pre_work(     void* field, oop new_val) { guarantee(false, "Not needed"); };
  97 protected:
  98   virtual void write_ref_field_pre_work(      oop* field, oop new_val) {};
  99   virtual void write_ref_field_pre_work(narrowOop* field, oop new_val) {};
 100 public:
 101 
 102   // ...then the post-write version.
 103   inline void write_ref_field(void* field, oop new_val, bool release = false);
 104 protected:
 105   virtual void write_ref_field_work(void* field, oop new_val, bool release = false) = 0;
 106 public:
 107 
 108   // Invoke the barrier, if any, necessary when writing the "bytes"-byte
 109   // value(s) "val1" (and "val2") into the primitive "field".
 110   virtual void write_prim_field(HeapWord* field, size_t bytes,
 111                                 juint val1, juint val2) = 0;
 112 
 113   // Operations on arrays, or general regions (e.g., for "clone") may be
 114   // optimized by some barriers.
 115 
 116   // The first six operations tell whether such an optimization exists for
 117   // the particular barrier.
 118   virtual bool has_read_ref_array_opt() = 0;
 119   virtual bool has_read_prim_array_opt() = 0;
 120   virtual bool has_write_ref_array_pre_opt() { return true; }
 121   virtual bool has_write_ref_array_opt() = 0;
 122   virtual bool has_write_prim_array_opt() = 0;
 123 
 124   virtual bool has_read_region_opt() = 0;
 125   virtual bool has_write_region_opt() = 0;
 126 
 127   // These operations should assert false unless the correponding operation
 128   // above returns true.  Otherwise, they should perform an appropriate
 129   // barrier for an array whose elements are all in the given memory region.
 130   virtual void read_ref_array(MemRegion mr) = 0;
 131   virtual void read_prim_array(MemRegion mr) = 0;
 132 
 133   // Below length is the # array elements being written
 134   virtual void write_ref_array_pre(oop* dst, int length,
 135                                    bool dest_uninitialized = false) {}
 136   virtual void write_ref_array_pre(narrowOop* dst, int length,
 137                                    bool dest_uninitialized = false) {}
 138   // Below count is the # array elements being written, starting
 139   // at the address "start", which may not necessarily be HeapWord-aligned
 140   inline void write_ref_array(HeapWord* start, size_t count);
 141 
 142   // Static versions, suitable for calling from generated code;
 143   // count is # array elements being written, starting with "start",
 144   // which may not necessarily be HeapWord-aligned.
 145   static void static_write_ref_array_pre(HeapWord* start, size_t count);
 146   static void static_write_ref_array_post(HeapWord* start, size_t count);
 147 
 148 protected:
 149   virtual void write_ref_array_work(MemRegion mr) = 0;
 150 public:
 151   virtual void write_prim_array(MemRegion mr) = 0;
 152 
 153   virtual void read_region(MemRegion mr) = 0;
 154 
 155   // (For efficiency reasons, this operation is specialized for certain
 156   // barrier types.  Semantically, it should be thought of as a call to the
 157   // virtual "_work" function below, which must implement the barrier.)
 158   inline void write_region(MemRegion mr);
 159 protected:
 160   virtual void write_region_work(MemRegion mr) = 0;
 161 public:
 162 
 163   // Some barrier sets create tables whose elements correspond to parts of
 164   // the heap; the CardTableModRefBS is an example.  Such barrier sets will
 165   // normally reserve space for such tables, and commit parts of the table
 166   // "covering" parts of the heap that are committed.  The constructor is
 167   // passed the maximum number of independently committable subregions to
 168   // be covered, and the "resize_covoered_region" function allows the
 169   // sub-parts of the heap to inform the barrier set of changes of their
 170   // sizes.
 171   BarrierSet(int max_covered_regions) :
 172     _max_covered_regions(max_covered_regions) {}
 173 
 174   // Inform the BarrierSet that the the covered heap region that starts
 175   // with "base" has been changed to have the given size (possibly from 0,
 176   // for initialization.)
 177   virtual void resize_covered_region(MemRegion new_region) = 0;
 178 
 179   // If the barrier set imposes any alignment restrictions on boundaries
 180   // within the heap, this function tells whether they are met.
 181   virtual bool is_aligned(HeapWord* addr) = 0;
 182 
 183   // Print a description of the memory for the barrier set
 184   virtual void print_on(outputStream* st) const = 0;
 185 };
 186 
 187 #endif // SHARE_VM_MEMORY_BARRIERSET_HPP
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