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   };
  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 protected:
  84   BarrierSet(const FakeRtti& fake_rtti) : _fake_rtti(fake_rtti) { }
  85   ~BarrierSet() { }
  86 
  87 public:
  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 
  96   // ...then the post-write version.
  97   inline void write_ref_field(void* field, oop new_val, bool release = false);
  98 
  99 protected:
 100   virtual void write_ref_field_pre_work(      oop* field, oop new_val) {};
 101   virtual void write_ref_field_pre_work(narrowOop* field, oop new_val) {};
 102   virtual void write_ref_field_work(void* field, oop new_val, bool release) = 0;
 103 
 104 public:
 105   // Operations on arrays, or general regions (e.g., for "clone") may be
 106   // optimized by some barriers.
 107 
 108   // Below length is the # array elements being written
 109   virtual void write_ref_array_pre(oop* dst, int length,
 110                                    bool dest_uninitialized = false) {}
 111   virtual void write_ref_array_pre(narrowOop* dst, int length,
 112                                    bool dest_uninitialized = false) {}
 113   // Below count is the # array elements being written, starting
 114   // at the address "start", which may not necessarily be HeapWord-aligned
 115   inline void write_ref_array(HeapWord* start, size_t count);
 116 
 117   // Static versions, suitable for calling from generated code;
 118   // count is # array elements being written, starting with "start",
 119   // which may not necessarily be HeapWord-aligned.
 120   static void static_write_ref_array_pre(HeapWord* start, size_t count);
 121   static void static_write_ref_array_post(HeapWord* start, size_t count);
 122 
 123   virtual void write_ref_nmethod_pre(oop* dst, nmethod* nm) {}
 124   virtual void write_ref_nmethod_post(oop* dst, nmethod* nm) {}
 125 
 126 protected:
 127   virtual void write_ref_array_work(MemRegion mr) = 0;
 128 
 129 public:
 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   void write_region(MemRegion mr);
 134 
 135 protected:
 136   virtual void write_region_work(MemRegion mr) = 0;
 137 
 138 public:
 139   // Inform the BarrierSet that the the covered heap region that starts
 140   // with "base" has been changed to have the given size (possibly from 0,
 141   // for initialization.)
 142   virtual void resize_covered_region(MemRegion new_region) = 0;
 143 
 144   // If the barrier set imposes any alignment restrictions on boundaries
 145   // within the heap, this function tells whether they are met.
 146   virtual bool is_aligned(HeapWord* addr) = 0;
 147 
 148   // Print a description of the memory for the barrier set
 149   virtual void print_on(outputStream* st) const = 0;
 150 };
 151 
 152 template<typename T>
 153 inline T* barrier_set_cast(BarrierSet* bs) {
 154   assert(bs->is_a(BarrierSet::GetName<T>::value), "wrong type of barrier set");
 155   return static_cast<T*>(bs);
 156 }
 157 
 158 #endif // SHARE_VM_GC_SHARED_BARRIERSET_HPP
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