clang  14.0.0git
RecordLayout.h
Go to the documentation of this file.
1 //===- RecordLayout.h - Layout information for a struct/union ---*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defines the RecordLayout interface.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_CLANG_AST_RECORDLAYOUT_H
14 #define LLVM_CLANG_AST_RECORDLAYOUT_H
15 
16 #include "clang/AST/ASTVector.h"
17 #include "clang/AST/CharUnits.h"
18 #include "clang/AST/DeclCXX.h"
19 #include "clang/Basic/LLVM.h"
20 #include "llvm/ADT/ArrayRef.h"
21 #include "llvm/ADT/DenseMap.h"
22 #include "llvm/ADT/PointerIntPair.h"
23 #include <cassert>
24 #include <cstdint>
25 
26 namespace clang {
27 
28 class ASTContext;
29 class CXXRecordDecl;
30 
31 /// ASTRecordLayout -
32 /// This class contains layout information for one RecordDecl,
33 /// which is a struct/union/class. The decl represented must be a definition,
34 /// not a forward declaration.
35 /// This class is also used to contain layout information for one
36 /// ObjCInterfaceDecl. FIXME - Find appropriate name.
37 /// These objects are managed by ASTContext.
39 public:
40  struct VBaseInfo {
41  /// The offset to this virtual base in the complete-object layout
42  /// of this class.
44 
45  private:
46  /// Whether this virtual base requires a vtordisp field in the
47  /// Microsoft ABI. These fields are required for certain operations
48  /// in constructors and destructors.
49  bool HasVtorDisp = false;
50 
51  public:
52  VBaseInfo() = default;
54  : VBaseOffset(VBaseOffset), HasVtorDisp(hasVtorDisp) {}
55 
56  bool hasVtorDisp() const { return HasVtorDisp; }
57  };
58 
59  using VBaseOffsetsMapTy = llvm::DenseMap<const CXXRecordDecl *, VBaseInfo>;
60 
61 private:
62  friend class ASTContext;
63 
64  /// Size - Size of record in characters.
65  CharUnits Size;
66 
67  /// DataSize - Size of record in characters without tail padding.
68  CharUnits DataSize;
69 
70  // Alignment - Alignment of record in characters.
71  CharUnits Alignment;
72 
73  // PreferredAlignment - Preferred alignment of record in characters. This
74  // can be different than Alignment in cases where it is beneficial for
75  // performance or backwards compatibility preserving (e.g. AIX-ABI).
76  CharUnits PreferredAlignment;
77 
78  // UnadjustedAlignment - Maximum of the alignments of the record members in
79  // characters.
80  CharUnits UnadjustedAlignment;
81 
82  /// RequiredAlignment - The required alignment of the object. In the MS-ABI
83  /// the __declspec(align()) trumps #pramga pack and must always be obeyed.
84  CharUnits RequiredAlignment;
85 
86  /// FieldOffsets - Array of field offsets in bits.
87  ASTVector<uint64_t> FieldOffsets;
88 
89  /// CXXRecordLayoutInfo - Contains C++ specific layout information.
90  struct CXXRecordLayoutInfo {
91  /// NonVirtualSize - The non-virtual size (in chars) of an object, which is
92  /// the size of the object without virtual bases.
93  CharUnits NonVirtualSize;
94 
95  /// NonVirtualAlignment - The non-virtual alignment (in chars) of an object,
96  /// which is the alignment of the object without virtual bases.
97  CharUnits NonVirtualAlignment;
98 
99  /// PreferredNVAlignment - The preferred non-virtual alignment (in chars) of
100  /// an object, which is the preferred alignment of the object without
101  /// virtual bases.
102  CharUnits PreferredNVAlignment;
103 
104  /// SizeOfLargestEmptySubobject - The size of the largest empty subobject
105  /// (either a base or a member). Will be zero if the class doesn't contain
106  /// any empty subobjects.
107  CharUnits SizeOfLargestEmptySubobject;
108 
109  /// VBPtrOffset - Virtual base table offset (Microsoft-only).
110  CharUnits VBPtrOffset;
111 
112  /// HasOwnVFPtr - Does this class provide a virtual function table
113  /// (vtable in Itanium, vftbl in Microsoft) that is independent from
114  /// its base classes?
115  bool HasOwnVFPtr : 1;
116 
117  /// HasVFPtr - Does this class have a vftable that could be extended by
118  /// a derived class. The class may have inherited this pointer from
119  /// a primary base class.
120  bool HasExtendableVFPtr : 1;
121 
122  /// EndsWithZeroSizedObject - True if this class contains a zero sized
123  /// member or base or a base with a zero sized member or base.
124  /// Only used for MS-ABI.
125  bool EndsWithZeroSizedObject : 1;
126 
127  /// True if this class is zero sized or first base is zero sized or
128  /// has this property. Only used for MS-ABI.
129  bool LeadsWithZeroSizedBase : 1;
130 
131  /// PrimaryBase - The primary base info for this record.
132  llvm::PointerIntPair<const CXXRecordDecl *, 1, bool> PrimaryBase;
133 
134  /// BaseSharingVBPtr - The base we share vbptr with.
135  const CXXRecordDecl *BaseSharingVBPtr;
136 
137  /// FIXME: This should really use a SmallPtrMap, once we have one in LLVM :)
138  using BaseOffsetsMapTy = llvm::DenseMap<const CXXRecordDecl *, CharUnits>;
139 
140  /// BaseOffsets - Contains a map from base classes to their offset.
141  BaseOffsetsMapTy BaseOffsets;
142 
143  /// VBaseOffsets - Contains a map from vbase classes to their offset.
144  VBaseOffsetsMapTy VBaseOffsets;
145  };
146 
147  /// CXXInfo - If the record layout is for a C++ record, this will have
148  /// C++ specific information about the record.
149  CXXRecordLayoutInfo *CXXInfo = nullptr;
150 
151  ASTRecordLayout(const ASTContext &Ctx, CharUnits size, CharUnits alignment,
152  CharUnits preferredAlignment, CharUnits unadjustedAlignment,
153  CharUnits requiredAlignment, CharUnits datasize,
154  ArrayRef<uint64_t> fieldoffsets);
155 
156  using BaseOffsetsMapTy = CXXRecordLayoutInfo::BaseOffsetsMapTy;
157 
158  // Constructor for C++ records.
159  ASTRecordLayout(const ASTContext &Ctx, CharUnits size, CharUnits alignment,
160  CharUnits preferredAlignment, CharUnits unadjustedAlignment,
161  CharUnits requiredAlignment, bool hasOwnVFPtr,
162  bool hasExtendableVFPtr, CharUnits vbptroffset,
163  CharUnits datasize, ArrayRef<uint64_t> fieldoffsets,
164  CharUnits nonvirtualsize, CharUnits nonvirtualalignment,
165  CharUnits preferrednvalignment,
166  CharUnits SizeOfLargestEmptySubobject,
167  const CXXRecordDecl *PrimaryBase, bool IsPrimaryBaseVirtual,
168  const CXXRecordDecl *BaseSharingVBPtr,
169  bool EndsWithZeroSizedObject, bool LeadsWithZeroSizedBase,
170  const BaseOffsetsMapTy &BaseOffsets,
171  const VBaseOffsetsMapTy &VBaseOffsets);
172 
173  ~ASTRecordLayout() = default;
174 
175  void Destroy(ASTContext &Ctx);
176 
177 public:
178  ASTRecordLayout(const ASTRecordLayout &) = delete;
179  ASTRecordLayout &operator=(const ASTRecordLayout &) = delete;
180 
181  /// getAlignment - Get the record alignment in characters.
182  CharUnits getAlignment() const { return Alignment; }
183 
184  /// getPreferredFieldAlignment - Get the record preferred alignment in
185  /// characters.
186  CharUnits getPreferredAlignment() const { return PreferredAlignment; }
187 
188  /// getUnadjustedAlignment - Get the record alignment in characters, before
189  /// alignment adjustement.
190  CharUnits getUnadjustedAlignment() const { return UnadjustedAlignment; }
191 
192  /// getSize - Get the record size in characters.
193  CharUnits getSize() const { return Size; }
194 
195  /// getFieldCount - Get the number of fields in the layout.
196  unsigned getFieldCount() const { return FieldOffsets.size(); }
197 
198  /// getFieldOffset - Get the offset of the given field index, in
199  /// bits.
200  uint64_t getFieldOffset(unsigned FieldNo) const {
201  return FieldOffsets[FieldNo];
202  }
203 
204  /// getDataSize() - Get the record data size, which is the record size
205  /// without tail padding, in characters.
206  CharUnits getDataSize() const { return DataSize; }
207 
208  /// getNonVirtualSize - Get the non-virtual size (in chars) of an object,
209  /// which is the size of the object without virtual bases.
211  assert(CXXInfo && "Record layout does not have C++ specific info!");
212 
213  return CXXInfo->NonVirtualSize;
214  }
215 
216  /// getNonVirtualAlignment - Get the non-virtual alignment (in chars) of an
217  /// object, which is the alignment of the object without virtual bases.
219  assert(CXXInfo && "Record layout does not have C++ specific info!");
220 
221  return CXXInfo->NonVirtualAlignment;
222  }
223 
224  /// getPreferredNVAlignment - Get the preferred non-virtual alignment (in
225  /// chars) of an object, which is the preferred alignment of the object
226  /// without virtual bases.
228  assert(CXXInfo && "Record layout does not have C++ specific info!");
229 
230  return CXXInfo->PreferredNVAlignment;
231  }
232 
233  /// getPrimaryBase - Get the primary base for this record.
234  const CXXRecordDecl *getPrimaryBase() const {
235  assert(CXXInfo && "Record layout does not have C++ specific info!");
236 
237  return CXXInfo->PrimaryBase.getPointer();
238  }
239 
240  /// isPrimaryBaseVirtual - Get whether the primary base for this record
241  /// is virtual or not.
242  bool isPrimaryBaseVirtual() const {
243  assert(CXXInfo && "Record layout does not have C++ specific info!");
244 
245  return CXXInfo->PrimaryBase.getInt();
246  }
247 
248  /// getBaseClassOffset - Get the offset, in chars, for the given base class.
250  assert(CXXInfo && "Record layout does not have C++ specific info!");
251 
252  Base = Base->getDefinition();
253  assert(CXXInfo->BaseOffsets.count(Base) && "Did not find base!");
254 
255  return CXXInfo->BaseOffsets[Base];
256  }
257 
258  /// getVBaseClassOffset - Get the offset, in chars, for the given base class.
260  assert(CXXInfo && "Record layout does not have C++ specific info!");
261 
262  VBase = VBase->getDefinition();
263  assert(CXXInfo->VBaseOffsets.count(VBase) && "Did not find base!");
264 
265  return CXXInfo->VBaseOffsets[VBase].VBaseOffset;
266  }
267 
269  assert(CXXInfo && "Record layout does not have C++ specific info!");
270  return CXXInfo->SizeOfLargestEmptySubobject;
271  }
272 
273  /// hasOwnVFPtr - Does this class provide its own virtual-function
274  /// table pointer, rather than inheriting one from a primary base
275  /// class? If so, it is at offset zero.
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 hasOwnVFPtr() const {
281  assert(CXXInfo && "Record layout does not have C++ specific info!");
282  return CXXInfo->HasOwnVFPtr;
283  }
284 
285  /// hasVFPtr - Does this class have a virtual function table pointer
286  /// that can be extended by a derived class? This is synonymous with
287  /// this class having a VFPtr at offset zero.
288  bool hasExtendableVFPtr() const {
289  assert(CXXInfo && "Record layout does not have C++ specific info!");
290  return CXXInfo->HasExtendableVFPtr;
291  }
292 
293  /// hasOwnVBPtr - Does this class provide its own virtual-base
294  /// table pointer, rather than inheriting one from a primary base
295  /// class?
296  ///
297  /// This implies that the ABI has no primary base class, meaning
298  /// that it has no base classes that are suitable under the conditions
299  /// of the ABI.
300  bool hasOwnVBPtr() const {
301  assert(CXXInfo && "Record layout does not have C++ specific info!");
302  return hasVBPtr() && !CXXInfo->BaseSharingVBPtr;
303  }
304 
305  /// hasVBPtr - Does this class have a virtual function table pointer.
306  bool hasVBPtr() const {
307  assert(CXXInfo && "Record layout does not have C++ specific info!");
308  return !CXXInfo->VBPtrOffset.isNegative();
309  }
310 
311  CharUnits getRequiredAlignment() const { return RequiredAlignment; }
312 
313  bool endsWithZeroSizedObject() const {
314  return CXXInfo && CXXInfo->EndsWithZeroSizedObject;
315  }
316 
317  bool leadsWithZeroSizedBase() const {
318  assert(CXXInfo && "Record layout does not have C++ specific info!");
319  return CXXInfo->LeadsWithZeroSizedBase;
320  }
321 
322  /// getVBPtrOffset - Get the offset for virtual base table pointer.
323  /// This is only meaningful with the Microsoft ABI.
325  assert(CXXInfo && "Record layout does not have C++ specific info!");
326  return CXXInfo->VBPtrOffset;
327  }
328 
330  assert(CXXInfo && "Record layout does not have C++ specific info!");
331  return CXXInfo->BaseSharingVBPtr;
332  }
333 
335  assert(CXXInfo && "Record layout does not have C++ specific info!");
336  return CXXInfo->VBaseOffsets;
337  }
338 };
339 
340 } // namespace clang
341 
342 #endif // LLVM_CLANG_AST_RECORDLAYOUT_H
clang::ASTRecordLayout::getPreferredAlignment
CharUnits getPreferredAlignment() const
getPreferredFieldAlignment - Get the record preferred alignment in characters.
Definition: RecordLayout.h:186
clang::ASTRecordLayout::getFieldOffset
uint64_t getFieldOffset(unsigned FieldNo) const
getFieldOffset - Get the offset of the given field index, in bits.
Definition: RecordLayout.h:200
clang::ASTRecordLayout::hasExtendableVFPtr
bool hasExtendableVFPtr() const
hasVFPtr - Does this class have a virtual function table pointer that can be extended by a derived cl...
Definition: RecordLayout.h:288
clang::CXXRecordDecl::getDefinition
CXXRecordDecl * getDefinition() const
Definition: DeclCXX.h:535
clang::ASTRecordLayout::getBaseClassOffset
CharUnits getBaseClassOffset(const CXXRecordDecl *Base) const
getBaseClassOffset - Get the offset, in chars, for the given base class.
Definition: RecordLayout.h:249
DeclCXX.h
clang::ASTRecordLayout::getNonVirtualAlignment
CharUnits getNonVirtualAlignment() const
getNonVirtualAlignment - Get the non-virtual alignment (in chars) of an object, which is the alignmen...
Definition: RecordLayout.h:218
clang::ASTRecordLayout::getSizeOfLargestEmptySubobject
CharUnits getSizeOfLargestEmptySubobject() const
Definition: RecordLayout.h:268
clang::ASTRecordLayout::getSize
CharUnits getSize() const
getSize - Get the record size in characters.
Definition: RecordLayout.h:193
clang::ASTRecordLayout::getUnadjustedAlignment
CharUnits getUnadjustedAlignment() const
getUnadjustedAlignment - Get the record alignment in characters, before alignment adjustement.
Definition: RecordLayout.h:190
clang::ASTRecordLayout::getPrimaryBase
const CXXRecordDecl * getPrimaryBase() const
getPrimaryBase - Get the primary base for this record.
Definition: RecordLayout.h:234
clang::ASTRecordLayout::getPreferredNVAlignment
CharUnits getPreferredNVAlignment() const
getPreferredNVAlignment - Get the preferred non-virtual alignment (in chars) of an object,...
Definition: RecordLayout.h:227
clang::ASTRecordLayout::VBaseInfo::VBaseInfo
VBaseInfo(CharUnits VBaseOffset, bool hasVtorDisp)
Definition: RecordLayout.h:53
clang::ASTContext
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:212
clang::ASTRecordLayout::VBaseInfo::hasVtorDisp
bool hasVtorDisp() const
Definition: RecordLayout.h:56
clang::ASTRecordLayout::getNonVirtualSize
CharUnits getNonVirtualSize() const
getNonVirtualSize - Get the non-virtual size (in chars) of an object, which is the size of the object...
Definition: RecordLayout.h:210
clang::ASTRecordLayout::VBaseInfo
Definition: RecordLayout.h:40
clang::ASTRecordLayout::operator=
ASTRecordLayout & operator=(const ASTRecordLayout &)=delete
clang::ASTRecordLayout::getVBPtrOffset
CharUnits getVBPtrOffset() const
getVBPtrOffset - Get the offset for virtual base table pointer.
Definition: RecordLayout.h:324
clang::ASTRecordLayout::getRequiredAlignment
CharUnits getRequiredAlignment() const
Definition: RecordLayout.h:311
Base
clang::ASTRecordLayout::leadsWithZeroSizedBase
bool leadsWithZeroSizedBase() const
Definition: RecordLayout.h:317
clang::ASTRecordLayout::VBaseInfo::VBaseInfo
VBaseInfo()=default
CharUnits.h
clang::ASTRecordLayout::getVBaseClassOffset
CharUnits getVBaseClassOffset(const CXXRecordDecl *VBase) const
getVBaseClassOffset - Get the offset, in chars, for the given base class.
Definition: RecordLayout.h:259
clang::ASTRecordLayout::isPrimaryBaseVirtual
bool isPrimaryBaseVirtual() const
isPrimaryBaseVirtual - Get whether the primary base for this record is virtual or not.
Definition: RecordLayout.h:242
clang::ASTRecordLayout::getDataSize
CharUnits getDataSize() const
getDataSize() - Get the record data size, which is the record size without tail padding,...
Definition: RecordLayout.h:206
clang::ASTVector< uint64_t >
clang::ASTRecordLayout
ASTRecordLayout - This class contains layout information for one RecordDecl, which is a struct/union/...
Definition: RecordLayout.h:38
clang::CXXRecordDecl
Represents a C++ struct/union/class.
Definition: DeclCXX.h:255
clang::ASTRecordLayout::getVBaseOffsetsMap
const VBaseOffsetsMapTy & getVBaseOffsetsMap() const
Definition: RecordLayout.h:334
clang::ASTRecordLayout::endsWithZeroSizedObject
bool endsWithZeroSizedObject() const
Definition: RecordLayout.h:313
clang::ASTRecordLayout::hasOwnVFPtr
bool hasOwnVFPtr() const
hasOwnVFPtr - Does this class provide its own virtual-function table pointer, rather than inheriting ...
Definition: RecordLayout.h:280
clang::ASTRecordLayout::VBaseOffsetsMapTy
llvm::DenseMap< const CXXRecordDecl *, VBaseInfo > VBaseOffsetsMapTy
Definition: RecordLayout.h:59
llvm::ArrayRef
Definition: LLVM.h:34
clang::ASTRecordLayout::hasOwnVBPtr
bool hasOwnVBPtr() const
hasOwnVBPtr - Does this class provide its own virtual-base table pointer, rather than inheriting one ...
Definition: RecordLayout.h:300
LLVM.h
clang::ASTRecordLayout::getBaseSharingVBPtr
const CXXRecordDecl * getBaseSharingVBPtr() const
Definition: RecordLayout.h:329
clang
Definition: CalledOnceCheck.h:17
clang::ASTRecordLayout::hasVBPtr
bool hasVBPtr() const
hasVBPtr - Does this class have a virtual function table pointer.
Definition: RecordLayout.h:306
clang::ASTRecordLayout::getFieldCount
unsigned getFieldCount() const
getFieldCount - Get the number of fields in the layout.
Definition: RecordLayout.h:196
clang::ASTRecordLayout::getAlignment
CharUnits getAlignment() const
getAlignment - Get the record alignment in characters.
Definition: RecordLayout.h:182
clang::CharUnits
CharUnits - This is an opaque type for sizes expressed in character units.
Definition: CharUnits.h:38
clang::ASTVector::size
size_type size() const
Definition: ASTVector.h:109
clang::ASTRecordLayout::VBaseInfo::VBaseOffset
CharUnits VBaseOffset
The offset to this virtual base in the complete-object layout of this class.
Definition: RecordLayout.h:43
ASTVector.h