heapRegionType.hpp revision 8413:92457dfb91bd 
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24
25#ifndef SHARE_VM_GC_G1_HEAPREGIONTYPE_HPP
26#define SHARE_VM_GC_G1_HEAPREGIONTYPE_HPP
27
28#include "memory/allocation.hpp"
29
30#define hrt_assert_is_valid(tag) \
31  assert(is_valid((tag)), err_msg("invalid HR type: %u", (uint) (tag)))
32
33class HeapRegionType VALUE_OBJ_CLASS_SPEC {
34private:
35  // We encode the value of the heap region type so the generation can be
36  // determined quickly. The tag is split into two parts:
37  //
38  //   major type (young, humongous)                         : top N-1 bits
39  //   minor type (eden / survivor, starts / cont hum, etc.) : bottom 1 bit
40  //
41  // If there's need to increase the number of minor types in the
42  // future, we'll have to increase the size of the latter and hence
43  // decrease the size of the former.
44  //
45  // 0000 0 [ 0] Free
46  //
47  // 0001 0      Young Mask
48  // 0001 0 [ 2] Eden
49  // 0001 1 [ 3] Survivor
50  //
51  // 0010 0      Humongous Mask
52  // 0010 0 [ 4] Starts Humongous
53  // 0010 1 [ 5] Continues Humongous
54  //
55  // 01000 [ 8] Old
56  typedef enum {
57    FreeTag               = 0,
58
59    YoungMask             = 2,
60    EdenTag               = YoungMask,
61    SurvTag               = YoungMask + 1,
62
63    HumongousMask         = 4,
64    StartsHumongousTag    = HumongousMask,
65    ContinuesHumongousTag = HumongousMask + 1,
66
67    OldTag                = 8
68  } Tag;
69
70  volatile Tag _tag;
71
72  static bool is_valid(Tag tag);
73
74  Tag get() const {
75    hrt_assert_is_valid(_tag);
76    return _tag;
77  }
78
79  // Sets the type to 'tag'.
80  void set(Tag tag) {
81    hrt_assert_is_valid(tag);
82    hrt_assert_is_valid(_tag);
83    _tag = tag;
84  }
85
86  // Sets the type to 'tag', expecting the type to be 'before'. This
87  // is available for when we want to add sanity checking to the type
88  // transition.
89  void set_from(Tag tag, Tag before) {
90    hrt_assert_is_valid(tag);
91    hrt_assert_is_valid(before);
92    hrt_assert_is_valid(_tag);
93    assert(_tag == before,
94           err_msg("HR tag: %u, expected: %u new tag; %u", _tag, before, tag));
95    _tag = tag;
96  }
97
98public:
99  // Queries
100
101  bool is_free() const { return get() == FreeTag; }
102
103  bool is_young()    const { return (get() & YoungMask) != 0; }
104  bool is_eden()     const { return get() == EdenTag;  }
105  bool is_survivor() const { return get() == SurvTag;  }
106
107  bool is_humongous()           const { return (get() & HumongousMask) != 0;   }
108  bool is_starts_humongous()    const { return get() == StartsHumongousTag;    }
109  bool is_continues_humongous() const { return get() == ContinuesHumongousTag; }
110
111  bool is_old() const { return get() == OldTag; }
112
113  // Setters
114
115  void set_free() { set(FreeTag); }
116
117  void set_eden()        { set_from(EdenTag, FreeTag); }
118  void set_eden_pre_gc() { set_from(EdenTag, SurvTag); }
119  void set_survivor()    { set_from(SurvTag, FreeTag); }
120
121  void set_starts_humongous()    { set_from(StartsHumongousTag,    FreeTag); }
122  void set_continues_humongous() { set_from(ContinuesHumongousTag, FreeTag); }
123
124  void set_old() { set(OldTag); }
125
126  // Misc
127
128  const char* get_str() const;
129  const char* get_short_str() const;
130
131  HeapRegionType() : _tag(FreeTag) { hrt_assert_is_valid(_tag); }
132};
133
134#endif // SHARE_VM_GC_G1_HEAPREGIONTYPE_HPP
135