clang  8.0.0svn
RecordLayout.h
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1 //===- RecordLayout.h - Layout information for a struct/union ---*- 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 RecordLayout interface.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_AST_RECORDLAYOUT_H
15 #define LLVM_CLANG_AST_RECORDLAYOUT_H
16 
17 #include "clang/AST/ASTVector.h"
18 #include "clang/AST/CharUnits.h"
19 #include "clang/AST/DeclCXX.h"
20 #include "clang/Basic/LLVM.h"
21 #include "llvm/ADT/ArrayRef.h"
22 #include "llvm/ADT/DenseMap.h"
23 #include "llvm/ADT/PointerIntPair.h"
24 #include <cassert>
25 #include <cstdint>
26 
27 namespace clang {
28 
29 class ASTContext;
30 class CXXRecordDecl;
31 
32 /// ASTRecordLayout -
33 /// This class contains layout information for one RecordDecl,
34 /// which is a struct/union/class. The decl represented must be a definition,
35 /// not a forward declaration.
36 /// This class is also used to contain layout information for one
37 /// ObjCInterfaceDecl. FIXME - Find appropriate name.
38 /// These objects are managed by ASTContext.
40 public:
41  struct VBaseInfo {
42  /// The offset to this virtual base in the complete-object layout
43  /// of this class.
45 
46  private:
47  /// Whether this virtual base requires a vtordisp field in the
48  /// Microsoft ABI. These fields are required for certain operations
49  /// in constructors and destructors.
50  bool HasVtorDisp = false;
51 
52  public:
53  VBaseInfo() = default;
54  VBaseInfo(CharUnits VBaseOffset, bool hasVtorDisp)
55  : VBaseOffset(VBaseOffset), HasVtorDisp(hasVtorDisp) {}
56 
57  bool hasVtorDisp() const { return HasVtorDisp; }
58  };
59 
60  using VBaseOffsetsMapTy = llvm::DenseMap<const CXXRecordDecl *, VBaseInfo>;
61 
62 private:
63  friend class ASTContext;
64 
65  /// Size - Size of record in characters.
66  CharUnits Size;
67 
68  /// DataSize - Size of record in characters without tail padding.
69  CharUnits DataSize;
70 
71  // Alignment - Alignment of record in characters.
72  CharUnits Alignment;
73 
74  // UnadjustedAlignment - Maximum of the alignments of the record members in
75  // characters.
76  CharUnits UnadjustedAlignment;
77 
78  /// RequiredAlignment - The required alignment of the object. In the MS-ABI
79  /// the __declspec(align()) trumps #pramga pack and must always be obeyed.
80  CharUnits RequiredAlignment;
81 
82  /// FieldOffsets - Array of field offsets in bits.
83  ASTVector<uint64_t> FieldOffsets;
84 
85  /// CXXRecordLayoutInfo - Contains C++ specific layout information.
86  struct CXXRecordLayoutInfo {
87  /// NonVirtualSize - The non-virtual size (in chars) of an object, which is
88  /// the size of the object without virtual bases.
89  CharUnits NonVirtualSize;
90 
91  /// NonVirtualAlignment - The non-virtual alignment (in chars) of an object,
92  /// which is the alignment of the object without virtual bases.
93  CharUnits NonVirtualAlignment;
94 
95  /// SizeOfLargestEmptySubobject - The size of the largest empty subobject
96  /// (either a base or a member). Will be zero if the class doesn't contain
97  /// any empty subobjects.
98  CharUnits SizeOfLargestEmptySubobject;
99 
100  /// VBPtrOffset - Virtual base table offset (Microsoft-only).
101  CharUnits VBPtrOffset;
102 
103  /// HasOwnVFPtr - Does this class provide a virtual function table
104  /// (vtable in Itanium, vftbl in Microsoft) that is independent from
105  /// its base classes?
106  bool HasOwnVFPtr : 1;
107 
108  /// HasVFPtr - Does this class have a vftable that could be extended by
109  /// a derived class. The class may have inherited this pointer from
110  /// a primary base class.
111  bool HasExtendableVFPtr : 1;
112 
113  /// EndsWithZeroSizedObject - True if this class contains a zero sized
114  /// member or base or a base with a zero sized member or base.
115  /// Only used for MS-ABI.
116  bool EndsWithZeroSizedObject : 1;
117 
118  /// True if this class is zero sized or first base is zero sized or
119  /// has this property. Only used for MS-ABI.
120  bool LeadsWithZeroSizedBase : 1;
121 
122  /// PrimaryBase - The primary base info for this record.
123  llvm::PointerIntPair<const CXXRecordDecl *, 1, bool> PrimaryBase;
124 
125  /// BaseSharingVBPtr - The base we share vbptr with.
126  const CXXRecordDecl *BaseSharingVBPtr;
127 
128  /// FIXME: This should really use a SmallPtrMap, once we have one in LLVM :)
129  using BaseOffsetsMapTy = llvm::DenseMap<const CXXRecordDecl *, CharUnits>;
130 
131  /// BaseOffsets - Contains a map from base classes to their offset.
132  BaseOffsetsMapTy BaseOffsets;
133 
134  /// VBaseOffsets - Contains a map from vbase classes to their offset.
135  VBaseOffsetsMapTy VBaseOffsets;
136  };
137 
138  /// CXXInfo - If the record layout is for a C++ record, this will have
139  /// C++ specific information about the record.
140  CXXRecordLayoutInfo *CXXInfo = nullptr;
141 
142  ASTRecordLayout(const ASTContext &Ctx, CharUnits size, CharUnits alignment,
143  CharUnits unadjustedAlignment,
144  CharUnits requiredAlignment, CharUnits datasize,
145  ArrayRef<uint64_t> fieldoffsets);
146 
147  using BaseOffsetsMapTy = CXXRecordLayoutInfo::BaseOffsetsMapTy;
148 
149  // Constructor for C++ records.
150  ASTRecordLayout(const ASTContext &Ctx,
151  CharUnits size, CharUnits alignment,
152  CharUnits unadjustedAlignment,
153  CharUnits requiredAlignment,
154  bool hasOwnVFPtr, bool hasExtendableVFPtr,
155  CharUnits vbptroffset,
156  CharUnits datasize,
157  ArrayRef<uint64_t> fieldoffsets,
158  CharUnits nonvirtualsize, CharUnits nonvirtualalignment,
159  CharUnits SizeOfLargestEmptySubobject,
160  const CXXRecordDecl *PrimaryBase,
161  bool IsPrimaryBaseVirtual,
162  const CXXRecordDecl *BaseSharingVBPtr,
163  bool EndsWithZeroSizedObject,
164  bool LeadsWithZeroSizedBase,
165  const BaseOffsetsMapTy& BaseOffsets,
166  const VBaseOffsetsMapTy& VBaseOffsets);
167 
168  ~ASTRecordLayout() = default;
169 
170  void Destroy(ASTContext &Ctx);
171 
172 public:
173  ASTRecordLayout(const ASTRecordLayout &) = delete;
174  ASTRecordLayout &operator=(const ASTRecordLayout &) = delete;
175 
176  /// getAlignment - Get the record alignment in characters.
177  CharUnits getAlignment() const { return Alignment; }
178 
179  /// getUnadjustedAlignment - Get the record alignment in characters, before
180  /// alignment adjustement.
181  CharUnits getUnadjustedAlignment() const { return UnadjustedAlignment; }
182 
183  /// getSize - Get the record size in characters.
184  CharUnits getSize() const { return Size; }
185 
186  /// getFieldCount - Get the number of fields in the layout.
187  unsigned getFieldCount() const { return FieldOffsets.size(); }
188 
189  /// getFieldOffset - Get the offset of the given field index, in
190  /// bits.
191  uint64_t getFieldOffset(unsigned FieldNo) const {
192  return FieldOffsets[FieldNo];
193  }
194 
195  /// getDataSize() - Get the record data size, which is the record size
196  /// without tail padding, in characters.
198  return DataSize;
199  }
200 
201  /// getNonVirtualSize - Get the non-virtual size (in chars) of an object,
202  /// which is the size of the object without virtual bases.
204  assert(CXXInfo && "Record layout does not have C++ specific info!");
205 
206  return CXXInfo->NonVirtualSize;
207  }
208 
209  /// getNonVirtualSize - Get the non-virtual alignment (in chars) of an object,
210  /// which is the alignment of the object without virtual bases.
212  assert(CXXInfo && "Record layout does not have C++ specific info!");
213 
214  return CXXInfo->NonVirtualAlignment;
215  }
216 
217  /// getPrimaryBase - Get the primary base for this record.
218  const CXXRecordDecl *getPrimaryBase() const {
219  assert(CXXInfo && "Record layout does not have C++ specific info!");
220 
221  return CXXInfo->PrimaryBase.getPointer();
222  }
223 
224  /// isPrimaryBaseVirtual - Get whether the primary base for this record
225  /// is virtual or not.
226  bool isPrimaryBaseVirtual() const {
227  assert(CXXInfo && "Record layout does not have C++ specific info!");
228 
229  return CXXInfo->PrimaryBase.getInt();
230  }
231 
232  /// getBaseClassOffset - Get the offset, in chars, for the given base class.
234  assert(CXXInfo && "Record layout does not have C++ specific info!");
235  assert(CXXInfo->BaseOffsets.count(Base) && "Did not find base!");
236 
237  return CXXInfo->BaseOffsets[Base];
238  }
239 
240  /// getVBaseClassOffset - Get the offset, in chars, for the given base class.
242  assert(CXXInfo && "Record layout does not have C++ specific info!");
243  assert(CXXInfo->VBaseOffsets.count(VBase) && "Did not find base!");
244 
245  return CXXInfo->VBaseOffsets[VBase].VBaseOffset;
246  }
247 
249  assert(CXXInfo && "Record layout does not have C++ specific info!");
250  return CXXInfo->SizeOfLargestEmptySubobject;
251  }
252 
253  /// hasOwnVFPtr - Does this class provide its own virtual-function
254  /// table pointer, rather than inheriting one from a primary base
255  /// class? If so, it is at offset zero.
256  ///
257  /// This implies that the ABI has no primary base class, meaning
258  /// that it has no base classes that are suitable under the conditions
259  /// of the ABI.
260  bool hasOwnVFPtr() const {
261  assert(CXXInfo && "Record layout does not have C++ specific info!");
262  return CXXInfo->HasOwnVFPtr;
263  }
264 
265  /// hasVFPtr - Does this class have a virtual function table pointer
266  /// that can be extended by a derived class? This is synonymous with
267  /// this class having a VFPtr at offset zero.
268  bool hasExtendableVFPtr() const {
269  assert(CXXInfo && "Record layout does not have C++ specific info!");
270  return CXXInfo->HasExtendableVFPtr;
271  }
272 
273  /// hasOwnVBPtr - Does this class provide its own virtual-base
274  /// table pointer, rather than inheriting one from a primary base
275  /// class?
276  ///
277  /// This implies that the ABI has no primary base class, meaning
278  /// that it has no base classes that are suitable under the conditions
279  /// of the ABI.
280  bool hasOwnVBPtr() const {
281  assert(CXXInfo && "Record layout does not have C++ specific info!");
282  return hasVBPtr() && !CXXInfo->BaseSharingVBPtr;
283  }
284 
285  /// hasVBPtr - Does this class have a virtual function table pointer.
286  bool hasVBPtr() const {
287  assert(CXXInfo && "Record layout does not have C++ specific info!");
288  return !CXXInfo->VBPtrOffset.isNegative();
289  }
290 
292  return RequiredAlignment;
293  }
294 
295  bool endsWithZeroSizedObject() const {
296  return CXXInfo && CXXInfo->EndsWithZeroSizedObject;
297  }
298 
299  bool leadsWithZeroSizedBase() const {
300  assert(CXXInfo && "Record layout does not have C++ specific info!");
301  return CXXInfo->LeadsWithZeroSizedBase;
302  }
303 
304  /// getVBPtrOffset - Get the offset for virtual base table pointer.
305  /// This is only meaningful with the Microsoft ABI.
307  assert(CXXInfo && "Record layout does not have C++ specific info!");
308  return CXXInfo->VBPtrOffset;
309  }
310 
312  assert(CXXInfo && "Record layout does not have C++ specific info!");
313  return CXXInfo->BaseSharingVBPtr;
314  }
315 
317  assert(CXXInfo && "Record layout does not have C++ specific info!");
318  return CXXInfo->VBaseOffsets;
319  }
320 };
321 
322 } // namespace clang
323 
324 #endif // LLVM_CLANG_AST_RECORDLAYOUT_H
bool isPrimaryBaseVirtual() const
isPrimaryBaseVirtual - Get whether the primary base for this record is virtual or not...
Definition: RecordLayout.h:226
CharUnits getBaseClassOffset(const CXXRecordDecl *Base) const
getBaseClassOffset - Get the offset, in chars, for the given base class.
Definition: RecordLayout.h:233
CharUnits getAlignment() const
getAlignment - Get the record alignment in characters.
Definition: RecordLayout.h:177
bool hasVBPtr() const
hasVBPtr - Does this class have a virtual function table pointer.
Definition: RecordLayout.h:286
bool hasOwnVFPtr() const
hasOwnVFPtr - Does this class provide its own virtual-function table pointer, rather than inheriting ...
Definition: RecordLayout.h:260
size_type size() const
Definition: ASTVector.h:109
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:153
CharUnits getVBaseClassOffset(const CXXRecordDecl *VBase) const
getVBaseClassOffset - Get the offset, in chars, for the given base class.
Definition: RecordLayout.h:241
CharUnits - This is an opaque type for sizes expressed in character units.
Definition: CharUnits.h:38
bool endsWithZeroSizedObject() const
Definition: RecordLayout.h:295
Forward-declares and imports various common LLVM datatypes that clang wants to use unqualified...
const VBaseOffsetsMapTy & getVBaseOffsetsMap() const
Definition: RecordLayout.h:316
ASTRecordLayout - This class contains layout information for one RecordDecl, which is a struct/union/...
Definition: RecordLayout.h:39
CharUnits getSizeOfLargestEmptySubobject() const
Definition: RecordLayout.h:248
const CXXRecordDecl * getPrimaryBase() const
getPrimaryBase - Get the primary base for this record.
Definition: RecordLayout.h:218
unsigned getFieldCount() const
getFieldCount - Get the number of fields in the layout.
Definition: RecordLayout.h:187
bool hasExtendableVFPtr() const
hasVFPtr - Does this class have a virtual function table pointer that can be extended by a derived cl...
Definition: RecordLayout.h:268
CharUnits getVBPtrOffset() const
getVBPtrOffset - Get the offset for virtual base table pointer.
Definition: RecordLayout.h:306
CharUnits getRequiredAlignment() const
Definition: RecordLayout.h:291
uint64_t getFieldOffset(unsigned FieldNo) const
getFieldOffset - Get the offset of the given field index, in bits.
Definition: RecordLayout.h:191
CharUnits getDataSize() const
getDataSize() - Get the record data size, which is the record size without tail padding, in characters.
Definition: RecordLayout.h:197
VBaseInfo(CharUnits VBaseOffset, bool hasVtorDisp)
Definition: RecordLayout.h:54
CharUnits getUnadjustedAlignment() const
getUnadjustedAlignment - Get the record alignment in characters, before alignment adjustement...
Definition: RecordLayout.h:181
CharUnits getNonVirtualAlignment() const
getNonVirtualSize - Get the non-virtual alignment (in chars) of an object, which is the alignment of ...
Definition: RecordLayout.h:211
Dataflow Directional Tag Classes.
CharUnits getSize() const
getSize - Get the record size in characters.
Definition: RecordLayout.h:184
const CXXRecordDecl * getBaseSharingVBPtr() const
Definition: RecordLayout.h:311
Defines the C++ Decl subclasses, other than those for templates (found in DeclTemplate.h) and friends (in DeclFriend.h).
Represents a C++ struct/union/class.
Definition: DeclCXX.h:308
CharUnits getNonVirtualSize() const
getNonVirtualSize - Get the non-virtual size (in chars) of an object, which is the size of the object...
Definition: RecordLayout.h:203
llvm::DenseMap< const CXXRecordDecl *, VBaseInfo > VBaseOffsetsMapTy
Definition: RecordLayout.h:60
CharUnits VBaseOffset
The offset to this virtual base in the complete-object layout of this class.
Definition: RecordLayout.h:44
ASTRecordLayout & operator=(const ASTRecordLayout &)=delete
bool hasOwnVBPtr() const
hasOwnVBPtr - Does this class provide its own virtual-base table pointer, rather than inheriting one ...
Definition: RecordLayout.h:280
bool leadsWithZeroSizedBase() const
Definition: RecordLayout.h:299