1 /*
   2  * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #ifndef HOTSPOT_EPSILONBARRIERSET_HPP_H
  25 #define HOTSPOT_EPSILONBARRIERSET_HPP_H
  26 
  27 #include "gc/shared/collectorPolicy.hpp"
  28 #include "gc/shared/barrierSet.hpp"
  29 
  30 // Most are no-ops.
  31 class EpsilonBarrierSet: public ModRefBarrierSet {
  32   friend class VMStructs;
  33 
  34 public:
  35   EpsilonBarrierSet() :
  36           ModRefBarrierSet(BarrierSet::FakeRtti(BarrierSet::Epsilon)) {};
  37 
  38   virtual bool has_write_ref_barrier()     { return false; }
  39   virtual bool has_write_ref_pre_barrier() { return false; }
  40   virtual bool has_write_ref_array_opt()   { return true; } // TODO: why?
  41   virtual bool has_write_region_opt()      { return true; } // TODO: why?
  42 
  43   virtual bool is_aligned(HeapWord *addr)  { return true; } // TODO: Safe?
  44 
  45   virtual void resize_covered_region(MemRegion new_region) {}
  46   virtual void print_on(outputStream *st) const {}
  47 
  48 protected:
  49   virtual void write_ref_field_work(void *field, oop new_val, bool release) {}
  50   virtual void write_ref_array_work(MemRegion mr) {}
  51   virtual void write_region_work(MemRegion mr) {}
  52 
  53 public:
  54   virtual void invalidate(MemRegion mr) {}
  55   virtual void clear(MemRegion mr) {}
  56 };
  57 
  58 template<>
  59 struct BarrierSet::GetName<EpsilonBarrierSet> {
  60   static const BarrierSet::Name value = BarrierSet::Epsilon;
  61 };
  62 
  63 #endif