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