1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  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).
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  24 
  25 #ifndef SHARE_VM_GC_SHARED_BARRIERSET_HPP
  26 #define SHARE_VM_GC_SHARED_BARRIERSET_HPP
  27 
  28 #include "memory/memRegion.hpp"
  29 #include "oops/oopsHierarchy.hpp"
  30 #include "utilities/fakeRttiSupport.hpp"
  31 
  32 // This class provides the interface between a barrier implementation and
  33 // the rest of the system.
  34 
  35 class BarrierSet: public CHeapObj<mtGC> {
  36   friend class VMStructs;
  37 public:
  38   // Fake RTTI support.  For a derived class T to participate
  39   // - T must have a corresponding Name entry.
  40   // - GetName<T> must be specialized to return the corresponding Name
  41   //   entry.
  42   // - If T is a base class, the constructor must have a FakeRtti
  43   //   parameter and pass it up to its base class, with the tag set
  44   //   augmented with the corresponding Name entry.
  45   // - If T is a concrete class, the constructor must create a
  46   //   FakeRtti object whose tag set includes the corresponding Name
  47   //   entry, and pass it up to its base class.
  48 
  49   enum Name {                   // associated class
  50     ModRef,                     // ModRefBarrierSet
  51     CardTableModRef,            // CardTableModRefBS
  52     CardTableForRS,             // CardTableModRefBSForCTRS
  53     CardTableExtension,         // CardTableExtension
  54     G1SATBCT,                   // G1SATBCardTableModRefBS
  55     G1SATBCTLogging,            // G1SATBCardTableLoggingModRefBS
  56     Epsilon,                    // EpsilonBarrierSet
  57   };
  58 
  59 protected:
  60   typedef FakeRttiSupport<BarrierSet, Name> FakeRtti;
  61 
  62 private:
  63   FakeRtti _fake_rtti;
  64 
  65   // Metafunction mapping a class derived from BarrierSet to the
  66   // corresponding Name enum tag.
  67   template<typename T> struct GetName;
  68 
  69   // Downcast argument to a derived barrier set type.
  70   // The cast is checked in a debug build.
  71   // T must have a specialization for BarrierSet::GetName<T>.
  72   template<typename T> friend T* barrier_set_cast(BarrierSet* bs);
  73 
  74 public:
  75   // Note: This is not presently the Name corresponding to the
  76   // concrete class of this object.
  77   BarrierSet::Name kind() const { return _fake_rtti.concrete_tag(); }
  78 
  79   // Test whether this object is of the type corresponding to bsn.
  80   bool is_a(BarrierSet::Name bsn) const { return _fake_rtti.has_tag(bsn); }
  81 
  82   // End of fake RTTI support.
  83 
  84 public:
  85   enum Flags {
  86     None                = 0,
  87     TargetUninitialized = 1
  88   };
  89 
  90 protected:
  91   // Some barrier sets create tables whose elements correspond to parts of
  92   // the heap; the CardTableModRefBS is an example.  Such barrier sets will
  93   // normally reserve space for such tables, and commit parts of the table
  94   // "covering" parts of the heap that are committed. At most one covered
  95   // region per generation is needed.
  96   static const int _max_covered_regions = 2;
  97 
  98   BarrierSet(const FakeRtti& fake_rtti) : _fake_rtti(fake_rtti) { }
  99   ~BarrierSet() { }
 100 
 101 public:
 102 
 103   // These operations indicate what kind of barriers the BarrierSet has.
 104   virtual bool has_read_ref_barrier() = 0;
 105   virtual bool has_read_prim_barrier() = 0;
 106   virtual bool has_write_ref_barrier() = 0;
 107   virtual bool has_write_ref_pre_barrier() = 0;
 108   virtual bool has_write_prim_barrier() = 0;
 109 
 110   // These functions indicate whether a particular access of the given
 111   // kinds requires a barrier.
 112   virtual bool read_ref_needs_barrier(void* field) = 0;
 113   virtual bool read_prim_needs_barrier(HeapWord* field, size_t bytes) = 0;
 114   virtual bool write_prim_needs_barrier(HeapWord* field, size_t bytes,
 115                                         juint val1, juint val2) = 0;
 116 
 117   // The first four operations provide a direct implementation of the
 118   // barrier set.  An interpreter loop, for example, could call these
 119   // directly, as appropriate.
 120 
 121   // Invoke the barrier, if any, necessary when reading the given ref field.
 122   virtual void read_ref_field(void* field) = 0;
 123 
 124   // Invoke the barrier, if any, necessary when reading the given primitive
 125   // "field" of "bytes" bytes in "obj".
 126   virtual void read_prim_field(HeapWord* field, size_t bytes) = 0;
 127 
 128   // Invoke the barrier, if any, necessary when writing "new_val" into the
 129   // ref field at "offset" in "obj".
 130   // (For efficiency reasons, this operation is specialized for certain
 131   // barrier types.  Semantically, it should be thought of as a call to the
 132   // virtual "_work" function below, which must implement the barrier.)
 133   // First the pre-write versions...
 134   template <class T> inline void write_ref_field_pre(T* field, oop new_val);
 135 private:
 136   // Helper for write_ref_field_pre and friends, testing for specialized cases.
 137   bool devirtualize_reference_writes() const;
 138 
 139   // Keep this private so as to catch violations at build time.
 140   virtual void write_ref_field_pre_work(     void* field, oop new_val) { guarantee(false, "Not needed"); };
 141 protected:
 142   virtual void write_ref_field_pre_work(      oop* field, oop new_val) {};
 143   virtual void write_ref_field_pre_work(narrowOop* field, oop new_val) {};
 144 public:
 145 
 146   // ...then the post-write version.
 147   inline void write_ref_field(void* field, oop new_val, bool release = false);
 148 protected:
 149   virtual void write_ref_field_work(void* field, oop new_val, bool release) = 0;
 150 public:
 151 
 152   // Invoke the barrier, if any, necessary when writing the "bytes"-byte
 153   // value(s) "val1" (and "val2") into the primitive "field".
 154   virtual void write_prim_field(HeapWord* field, size_t bytes,
 155                                 juint val1, juint val2) = 0;
 156 
 157   // Operations on arrays, or general regions (e.g., for "clone") may be
 158   // optimized by some barriers.
 159 
 160   // The first six operations tell whether such an optimization exists for
 161   // the particular barrier.
 162   virtual bool has_read_ref_array_opt() = 0;
 163   virtual bool has_read_prim_array_opt() = 0;
 164   virtual bool has_write_ref_array_pre_opt() { return true; }
 165   virtual bool has_write_ref_array_opt() = 0;
 166   virtual bool has_write_prim_array_opt() = 0;
 167 
 168   virtual bool has_read_region_opt() = 0;
 169   virtual bool has_write_region_opt() = 0;
 170 
 171   // These operations should assert false unless the corresponding operation
 172   // above returns true.  Otherwise, they should perform an appropriate
 173   // barrier for an array whose elements are all in the given memory region.
 174   virtual void read_ref_array(MemRegion mr) = 0;
 175   virtual void read_prim_array(MemRegion mr) = 0;
 176 
 177   // Below length is the # array elements being written
 178   virtual void write_ref_array_pre(oop* dst, int length,
 179                                    bool dest_uninitialized = false) {}
 180   virtual void write_ref_array_pre(narrowOop* dst, int length,
 181                                    bool dest_uninitialized = false) {}
 182   // Below count is the # array elements being written, starting
 183   // at the address "start", which may not necessarily be HeapWord-aligned
 184   inline void write_ref_array(HeapWord* start, size_t count);
 185 
 186   // Static versions, suitable for calling from generated code;
 187   // count is # array elements being written, starting with "start",
 188   // which may not necessarily be HeapWord-aligned.
 189   static void static_write_ref_array_pre(HeapWord* start, size_t count);
 190   static void static_write_ref_array_post(HeapWord* start, size_t count);
 191 
 192   virtual void write_ref_nmethod_pre(oop* dst, nmethod* nm) {}
 193   virtual void write_ref_nmethod_post(oop* dst, nmethod* nm) {}
 194 
 195 protected:
 196   virtual void write_ref_array_work(MemRegion mr) = 0;
 197 public:
 198   virtual void write_prim_array(MemRegion mr) = 0;
 199 
 200   virtual void read_region(MemRegion mr) = 0;
 201 
 202   // (For efficiency reasons, this operation is specialized for certain
 203   // barrier types.  Semantically, it should be thought of as a call to the
 204   // virtual "_work" function below, which must implement the barrier.)
 205   void write_region(MemRegion mr);
 206 protected:
 207   virtual void write_region_work(MemRegion mr) = 0;
 208 public:
 209   // Inform the BarrierSet that the the covered heap region that starts
 210   // with "base" has been changed to have the given size (possibly from 0,
 211   // for initialization.)
 212   virtual void resize_covered_region(MemRegion new_region) = 0;
 213 
 214   // If the barrier set imposes any alignment restrictions on boundaries
 215   // within the heap, this function tells whether they are met.
 216   virtual bool is_aligned(HeapWord* addr) = 0;
 217 
 218   // Print a description of the memory for the barrier set
 219   virtual void print_on(outputStream* st) const = 0;
 220 };
 221 
 222 template<typename T>
 223 inline T* barrier_set_cast(BarrierSet* bs) {
 224   assert(bs->is_a(BarrierSet::GetName<T>::value), "wrong type of barrier set");
 225   return static_cast<T*>(bs);
 226 }
 227 
 228 #endif // SHARE_VM_GC_SHARED_BARRIERSET_HPP
--- EOF ---