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 class EpsilonBarrierSet: public ModRefBarrierSet {
  31   friend class VMStructs;
  32 
  33 public:
  34   EpsilonBarrierSet() :
  35           ModRefBarrierSet(BarrierSet::FakeRtti(BarrierSet::Epsilon)) {};
  36 
  37   virtual bool has_write_ref_pre_barrier() {
  38     return false;
  39   }
  40 
  41   virtual bool has_write_ref_array_opt() {
  42     return true; // TODO: why?
  43   }
  44 
  45   virtual bool has_write_region_opt() {
  46     return true; // TODO: why?
  47   }
  48 
  49   virtual void resize_covered_region(MemRegion new_region) {
  50 
  51   }
  52 
  53   virtual bool is_aligned(HeapWord *addr) {
  54     return true;
  55   }
  56 
  57   virtual void print_on(outputStream *st) const {
  58     // do nothing
  59   }
  60 
  61 protected:
  62   virtual void write_ref_field_work(void *field, oop new_val, bool release) {
  63     // do nothing
  64   }
  65 
  66   virtual void write_ref_array_work(MemRegion mr) {
  67     // do nothing
  68   }
  69 
  70   virtual void write_region_work(MemRegion mr) {
  71     // do nothing
  72   }
  73 
  74 public:
  75   virtual void invalidate(MemRegion mr) {
  76 
  77   }
  78 
  79   virtual void clear(MemRegion mr) {
  80 
  81   }
  82 };
  83 
  84 template<>
  85 struct BarrierSet::GetName<EpsilonBarrierSet> {
  86   static const BarrierSet::Name value = BarrierSet::Epsilon;
  87 };
  88 
  89 #endif