1 /*

     2  * Copyright (c) 2000, 2015, 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_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   // Keep this private so as to catch violations at build time.

   136   virtual void write_ref_field_pre_work(     void* field, oop new_val) { guarantee(false, "Not needed"); };

   137 protected:

   138   virtual void write_ref_field_pre_work(      oop* field, oop new_val) {};

   139   virtual void write_ref_field_pre_work(narrowOop* field, oop new_val) {};

   140 public:

   141 

   142   // ...then the post-write version.

   143   inline void write_ref_field(void* field, oop new_val, bool release = false);

   144 protected:

   145   virtual void write_ref_field_work(void* field, oop new_val, bool release = false) = 0;

   146 public:

   147 

   148   // Invoke the barrier, if any, necessary when writing the "bytes"-byte

   149   // value(s) "val1" (and "val2") into the primitive "field".

   150   virtual void write_prim_field(HeapWord* field, size_t bytes,

   151                                 juint val1, juint val2) = 0;

   152 

   153   // Operations on arrays, or general regions (e.g., for "clone") may be

   154   // optimized by some barriers.

   155 

   156   // The first six operations tell whether such an optimization exists for

   157   // the particular barrier.

   158   virtual bool has_read_ref_array_opt() = 0;

   159   virtual bool has_read_prim_array_opt() = 0;

   160   virtual bool has_write_ref_array_pre_opt() { return true; }

   161   virtual bool has_write_ref_array_opt() = 0;

   162   virtual bool has_write_prim_array_opt() = 0;

   163 

   164   virtual bool has_read_region_opt() = 0;

   165   virtual bool has_write_region_opt() = 0;

   166 

   167   // These operations should assert false unless the corresponding operation

   168   // above returns true.  Otherwise, they should perform an appropriate

   169   // barrier for an array whose elements are all in the given memory region.

   170   virtual void read_ref_array(MemRegion mr) = 0;

   171   virtual void read_prim_array(MemRegion mr) = 0;

   172 

   173   // Below length is the # array elements being written

   174   virtual void write_ref_array_pre(oop* dst, int length,

   175                                    bool dest_uninitialized = false) {}

   176   virtual void write_ref_array_pre(narrowOop* dst, int length,

   177                                    bool dest_uninitialized = false) {}

   178   // Below count is the # array elements being written, starting

   179   // at the address "start", which may not necessarily be HeapWord-aligned

   180   inline void write_ref_array(HeapWord* start, size_t count);

   181 

   182   // Static versions, suitable for calling from generated code;

   183   // count is # array elements being written, starting with "start",

   184   // which may not necessarily be HeapWord-aligned.

   185   static void static_write_ref_array_pre(HeapWord* start, size_t count);

   186   static void static_write_ref_array_post(HeapWord* start, size_t count);

   187 

   188 protected:

   189   virtual void write_ref_array_work(MemRegion mr) = 0;

   190 public:

   191   virtual void write_prim_array(MemRegion mr) = 0;

   192 

   193   virtual void read_region(MemRegion mr) = 0;

   194 

   195   // (For efficiency reasons, this operation is specialized for certain

   196   // barrier types.  Semantically, it should be thought of as a call to the

   197   // virtual "_work" function below, which must implement the barrier.)

   198   void write_region(MemRegion mr);

   199 protected:

   200   virtual void write_region_work(MemRegion mr) = 0;

   201 public:

   202   // Inform the BarrierSet that the the covered heap region that starts

   203   // with "base" has been changed to have the given size (possibly from 0,

   204   // for initialization.)

   205   virtual void resize_covered_region(MemRegion new_region) = 0;

   206 

   207   // If the barrier set imposes any alignment restrictions on boundaries

   208   // within the heap, this function tells whether they are met.

   209   virtual bool is_aligned(HeapWord* addr) = 0;

   210 

   211   // Print a description of the memory for the barrier set

   212   virtual void print_on(outputStream* st) const = 0;

   213 };

   214 

   215 template<typename T>

   216 inline T* barrier_set_cast(BarrierSet* bs) {

   217   assert(bs->is_a(BarrierSet::GetName<T>::value), "wrong type of barrier set");

   218   return static_cast<T*>(bs);

   219 }

   220 

   221 #endif // SHARE_VM_GC_SHARED_BARRIERSET_HPP