1 | //===--- AlignOf.h - Portable calculation of type alignment -----*- C++ -*-===// |
2 | // |
3 | // The LLVM Compiler Infrastructure |
4 | // |
5 | // This file is distributed under the University of Illinois Open Source |
6 | // License. See LICENSE.TXT for details. |
7 | // |
8 | //===----------------------------------------------------------------------===// |
9 | // |
10 | // This file defines the AlignedCharArray and AlignedCharArrayUnion classes. |
11 | // |
12 | //===----------------------------------------------------------------------===// |
13 | |
14 | // ATen: modified from llvm::AlignOf |
15 | // replaced LLVM_ALIGNAS with alignas |
16 | |
17 | #pragma once |
18 | |
19 | #include <cstddef> |
20 | |
21 | namespace c10 { |
22 | |
23 | /// \struct AlignedCharArray |
24 | /// \brief Helper for building an aligned character array type. |
25 | /// |
26 | /// This template is used to explicitly build up a collection of aligned |
27 | /// character array types. We have to build these up using a macro and explicit |
28 | /// specialization to cope with MSVC (at least till 2015) where only an |
29 | /// integer literal can be used to specify an alignment constraint. Once built |
30 | /// up here, we can then begin to indirect between these using normal C++ |
31 | /// template parameters. |
32 | |
33 | // MSVC requires special handling here. |
34 | #ifndef _MSC_VER |
35 | |
36 | template <size_t Alignment, size_t Size> |
37 | struct AlignedCharArray { |
38 | alignas(Alignment) char buffer[Size]; |
39 | }; |
40 | |
41 | #else // _MSC_VER |
42 | |
43 | /// \brief Create a type with an aligned char buffer. |
44 | template <size_t Alignment, size_t Size> |
45 | struct AlignedCharArray; |
46 | |
47 | // We provide special variations of this template for the most common |
48 | // alignments because __declspec(align(...)) doesn't actually work when it is |
49 | // a member of a by-value function argument in MSVC, even if the alignment |
50 | // request is something reasonably like 8-byte or 16-byte. Note that we can't |
51 | // even include the declspec with the union that forces the alignment because |
52 | // MSVC warns on the existence of the declspec despite the union member forcing |
53 | // proper alignment. |
54 | |
55 | template <size_t Size> |
56 | struct AlignedCharArray<1, Size> { |
57 | union { |
58 | char aligned; |
59 | char buffer[Size]; |
60 | }; |
61 | }; |
62 | |
63 | template <size_t Size> |
64 | struct AlignedCharArray<2, Size> { |
65 | union { |
66 | short aligned; |
67 | char buffer[Size]; |
68 | }; |
69 | }; |
70 | |
71 | template <size_t Size> |
72 | struct AlignedCharArray<4, Size> { |
73 | union { |
74 | int aligned; |
75 | char buffer[Size]; |
76 | }; |
77 | }; |
78 | |
79 | template <size_t Size> |
80 | struct AlignedCharArray<8, Size> { |
81 | union { |
82 | double aligned; |
83 | char buffer[Size]; |
84 | }; |
85 | }; |
86 | |
87 | // The rest of these are provided with a __declspec(align(...)) and we simply |
88 | // can't pass them by-value as function arguments on MSVC. |
89 | |
90 | #define AT_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \ |
91 | template <size_t Size> \ |
92 | struct AlignedCharArray<x, Size> { \ |
93 | __declspec(align(x)) char buffer[Size]; \ |
94 | }; |
95 | |
96 | AT_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(16) |
97 | AT_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(32) |
98 | AT_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(64) |
99 | AT_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(128) |
100 | |
101 | #undef AT_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT |
102 | |
103 | #endif // _MSC_VER |
104 | |
105 | namespace detail { |
106 | template < |
107 | typename T1, |
108 | typename T2 = char, |
109 | typename T3 = char, |
110 | typename T4 = char, |
111 | typename T5 = char, |
112 | typename T6 = char, |
113 | typename T7 = char, |
114 | typename T8 = char, |
115 | typename T9 = char, |
116 | typename T10 = char> |
117 | class AlignerImpl { |
118 | T1 t1; |
119 | T2 t2; |
120 | T3 t3; |
121 | T4 t4; |
122 | T5 t5; |
123 | T6 t6; |
124 | T7 t7; |
125 | T8 t8; |
126 | T9 t9; |
127 | T10 t10; |
128 | |
129 | public: |
130 | AlignerImpl() = delete; |
131 | }; |
132 | |
133 | template < |
134 | typename T1, |
135 | typename T2 = char, |
136 | typename T3 = char, |
137 | typename T4 = char, |
138 | typename T5 = char, |
139 | typename T6 = char, |
140 | typename T7 = char, |
141 | typename T8 = char, |
142 | typename T9 = char, |
143 | typename T10 = char> |
144 | union SizerImpl { |
145 | char arr1[sizeof(T1)], arr2[sizeof(T2)], arr3[sizeof(T3)], arr4[sizeof(T4)], |
146 | arr5[sizeof(T5)], arr6[sizeof(T6)], arr7[sizeof(T7)], arr8[sizeof(T8)], |
147 | arr9[sizeof(T9)], arr10[sizeof(T10)]; |
148 | }; |
149 | } // end namespace detail |
150 | |
151 | /// \brief This union template exposes a suitably aligned and sized character |
152 | /// array member which can hold elements of any of up to ten types. |
153 | /// |
154 | /// These types may be arrays, structs, or any other types. The goal is to |
155 | /// expose a char array buffer member which can be used as suitable storage for |
156 | /// a placement new of any of these types. Support for more than ten types can |
157 | /// be added at the cost of more boilerplate. |
158 | template < |
159 | typename T1, |
160 | typename T2 = char, |
161 | typename T3 = char, |
162 | typename T4 = char, |
163 | typename T5 = char, |
164 | typename T6 = char, |
165 | typename T7 = char, |
166 | typename T8 = char, |
167 | typename T9 = char, |
168 | typename T10 = char> |
169 | struct AlignedCharArrayUnion |
170 | : AlignedCharArray< |
171 | alignof(detail::AlignerImpl<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>), |
172 | sizeof(::c10::detail:: |
173 | SizerImpl<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>)> {}; |
174 | } // end namespace c10 |
175 | |