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32 | 32 | // WordSize is used for sizes measured in machine words (i.e., 32bit or 64bit words |
33 | 33 | // depending on platform). |
34 | 34 | // |
35 | | -// The classes are defined with friend functions operating on them instead of member |
36 | | -// functions so that they (the classes) can be re-#define'd to int types in optimized |
37 | | -// mode. This allows full type checking and maximum safety in debug mode, and full |
38 | | -// optimizations (constant folding) and zero overhead (time and space wise) in the |
39 | | -// optimized build (some compilers do not optimize one-element value classes but |
40 | | -// instead create an object in memory - thus the overhead may be significant). |
41 | | -// |
42 | | -// Note: 1) DO NOT add new overloaded friend functions that do not have a unique function |
43 | | -// function name but require signature types for resolution. This will not work |
44 | | -// in optimized mode as both, ByteSize and WordSize are mapped to the same type |
45 | | -// and thus the distinction would not be possible anymore (=> compiler errors). |
46 | | -// |
47 | | -// 2) DO NOT add non-static member functions as they cannot be mapped so something |
48 | | -// compilable in the optimized build. Static member functions could be added |
49 | | -// but require a corresponding class definition in the optimized build. |
50 | | -// |
51 | 35 | // These classes should help doing a transition from (currently) word-size based offsets |
52 | 36 | // to byte-size based offsets in the VM (this will be important if we desire to pack |
53 | 37 | // objects more densely in the VM for 64bit machines). Such a transition should proceed |
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56 | 40 | // a) first transition the whole VM into a form where all sizes are strongly typed |
57 | 41 | // b) change all WordSize's to ByteSize's where desired and fix the compilation errors |
58 | 42 |
|
| 43 | +enum class WordSize : int {}; |
59 | 44 |
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60 | | -#ifdef ASSERT |
61 | | - |
62 | | -class ByteSize { |
63 | | - private: |
64 | | - int _size; |
65 | | - |
66 | | - // Note: This constructor must be private to avoid implicit conversions! |
67 | | - ByteSize(int size) { _size = size; } |
68 | | - |
69 | | - public: |
70 | | - // constructors |
71 | | - inline friend ByteSize in_ByteSize(int size); |
72 | | - |
73 | | - // accessors |
74 | | - inline friend int in_bytes(ByteSize x); |
75 | | - |
76 | | - // operators |
77 | | - friend ByteSize operator + (ByteSize x, ByteSize y) { return ByteSize(in_bytes(x) + in_bytes(y)); } |
78 | | - friend ByteSize operator - (ByteSize x, ByteSize y) { return ByteSize(in_bytes(x) - in_bytes(y)); } |
79 | | - friend ByteSize operator * (ByteSize x, int y) { return ByteSize(in_bytes(x) * y ); } |
80 | | - |
81 | | - // comparison |
82 | | - friend bool operator == (ByteSize x, ByteSize y) { return in_bytes(x) == in_bytes(y); } |
83 | | - friend bool operator != (ByteSize x, ByteSize y) { return in_bytes(x) != in_bytes(y); } |
84 | | - friend bool operator < (ByteSize x, ByteSize y) { return in_bytes(x) < in_bytes(y); } |
85 | | - friend bool operator <= (ByteSize x, ByteSize y) { return in_bytes(x) <= in_bytes(y); } |
86 | | - friend bool operator > (ByteSize x, ByteSize y) { return in_bytes(x) > in_bytes(y); } |
87 | | - friend bool operator >= (ByteSize x, ByteSize y) { return in_bytes(x) >= in_bytes(y); } |
88 | | -}; |
89 | | - |
90 | | -inline ByteSize in_ByteSize(int size) { return ByteSize(size); } |
91 | | -inline int in_bytes(ByteSize x) { return x._size; } |
92 | | - |
93 | | - |
94 | | -class WordSize { |
95 | | - private: |
96 | | - int _size; |
97 | | - |
98 | | - // Note: This constructor must be private to avoid implicit conversions! |
99 | | - WordSize(int size) { _size = size; } |
100 | | - |
101 | | - public: |
102 | | - // constructors |
103 | | - inline friend WordSize in_WordSize(int size); |
104 | | - |
105 | | - // accessors |
106 | | - inline friend int in_words(WordSize x); |
107 | | - |
108 | | - // operators |
109 | | - friend WordSize operator + (WordSize x, WordSize y) { return WordSize(in_words(x) + in_words(y)); } |
110 | | - friend WordSize operator - (WordSize x, WordSize y) { return WordSize(in_words(x) - in_words(y)); } |
111 | | - friend WordSize operator * (WordSize x, int y) { return WordSize(in_words(x) * y ); } |
112 | | - |
113 | | - // comparison |
114 | | - friend bool operator == (WordSize x, WordSize y) { return in_words(x) == in_words(y); } |
115 | | - friend bool operator != (WordSize x, WordSize y) { return in_words(x) != in_words(y); } |
116 | | - friend bool operator < (WordSize x, WordSize y) { return in_words(x) < in_words(y); } |
117 | | - friend bool operator <= (WordSize x, WordSize y) { return in_words(x) <= in_words(y); } |
118 | | - friend bool operator > (WordSize x, WordSize y) { return in_words(x) > in_words(y); } |
119 | | - friend bool operator >= (WordSize x, WordSize y) { return in_words(x) >= in_words(y); } |
120 | | -}; |
121 | | - |
122 | | -inline WordSize in_WordSize(int size) { return WordSize(size); } |
123 | | -inline int in_words(WordSize x) { return x._size; } |
124 | | - |
125 | | - |
126 | | -#else // ASSERT |
127 | | - |
128 | | -// The following definitions must match the corresponding friend declarations |
129 | | -// in the Byte/WordSize classes if they are typedef'ed to be int. This will |
130 | | -// be the case in optimized mode to ensure zero overhead for these types. |
131 | | -// |
132 | | -// Note: If a compiler does not inline these function calls away, one may |
133 | | -// want to use #define's to make sure full optimization (constant |
134 | | -// folding in particular) is possible. |
135 | | - |
136 | | -typedef int ByteSize; |
137 | | -inline ByteSize in_ByteSize(int size) { return size; } |
138 | | -inline int in_bytes (ByteSize x) { return x; } |
| 45 | +constexpr WordSize in_WordSize(int size) { return static_cast<WordSize>(size); } |
| 46 | +constexpr int in_words(WordSize x) { return static_cast<int>(x); } |
139 | 47 |
|
140 | | -typedef int WordSize; |
141 | | -inline WordSize in_WordSize(int size) { return size; } |
142 | | -inline int in_words (WordSize x) { return x; } |
| 48 | +enum class ByteSize : int {}; |
143 | 49 |
|
144 | | -#endif // ASSERT |
| 50 | +constexpr ByteSize in_ByteSize(int size) { return static_cast<ByteSize>(size); } |
| 51 | +constexpr int in_bytes(ByteSize x) { return static_cast<int>(x); } |
145 | 52 |
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| 53 | +constexpr ByteSize operator + (ByteSize x, ByteSize y) { return in_ByteSize(in_bytes(x) + in_bytes(y)); } |
| 54 | +constexpr ByteSize operator - (ByteSize x, ByteSize y) { return in_ByteSize(in_bytes(x) - in_bytes(y)); } |
| 55 | +constexpr ByteSize operator * (ByteSize x, int y) { return in_ByteSize(in_bytes(x) * y ); } |
146 | 56 |
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147 | 57 | // Use the following #define to get C++ field member offsets |
148 | 58 |
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