1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_
18#define ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_
19
20#include "base/macros.h"
21#include "base/mutex.h"
22
23namespace art {
24namespace mirror {
25class Object;
26}  // namespace mirror
27namespace gc {
28namespace space {
29class ContinuousSpace;
30}  // namespace space
31
32namespace collector {
33
34// An immune region is a continuous region of memory for which all objects contained are assumed to
35// be marked. This is used as an optimization in the GC to avoid needing to test the mark bitmap of
36// the zygote, image spaces, and sometimes non moving spaces. Doing the ContainsObject check is
37// faster than doing a bitmap read. There is no support for discontinuous spaces and you need to be
38// careful that your immune region doesn't contain any large objects.
39class ImmuneRegion {
40 public:
41  ImmuneRegion();
42
43  void Reset();
44
45  // Returns true if an object is inside of the immune region (assumed to be marked).
46  ALWAYS_INLINE bool ContainsObject(const mirror::Object* obj) const {
47    // Note: Relies on integer underflow behavior.
48    return reinterpret_cast<uintptr_t>(obj) - reinterpret_cast<uintptr_t>(begin_) < size_;
49  }
50
51  void SetBegin(mirror::Object* begin) {
52    begin_ = begin;
53    UpdateSize();
54  }
55
56  void SetEnd(mirror::Object* end) {
57    end_ = end;
58    UpdateSize();
59  }
60
61  mirror::Object* Begin() const {
62    return begin_;
63  }
64
65  mirror::Object* End() const {
66    return end_;
67  }
68
69  size_t Size() const {
70    return size_;
71  }
72
73 private:
74  void UpdateSize() {
75    size_ = reinterpret_cast<uintptr_t>(end_) - reinterpret_cast<uintptr_t>(begin_);
76  }
77
78  mirror::Object* begin_;
79  mirror::Object* end_;
80  uintptr_t size_;
81};
82
83}  // namespace collector
84}  // namespace gc
85}  // namespace art
86
87#endif  // ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_
88