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
26namespace clang {
27
28class ASTContext;
29class 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.
38class ASTRecordLayout {
39public:
40  struct VBaseInfo {
41    /// The offset to this virtual base in the complete-object layout
42    /// of this class.
43    CharUnits VBaseOffset;
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;
53    VBaseInfo(CharUnits VBaseOffset, bool hasVtorDisp)
54        : VBaseOffset(VBaseOffset), HasVtorDisp(hasVtorDisp) {}
55
56    bool hasVtorDisp() const { return HasVtorDisp; }
57  };
58
59  using VBaseOffsetsMapTy = llvm::DenseMap<const CXXRecordDecl *, VBaseInfo>;
60
61private:
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
177public:
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.
210  CharUnits getNonVirtualSize() const {
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.
218  CharUnits getNonVirtualAlignment() const {
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.
227  CharUnits getPreferredNVAlignment() const {
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.
249  CharUnits getBaseClassOffset(const CXXRecordDecl *Base) const {
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.
259  CharUnits getVBaseClassOffset(const CXXRecordDecl *VBase) const {
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
268  CharUnits getSizeOfLargestEmptySubobject() const {
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.
324  CharUnits getVBPtrOffset() const {
325    assert(CXXInfo && "Record layout does not have C++ specific info!");
326    return CXXInfo->VBPtrOffset;
327  }
328
329  const CXXRecordDecl *getBaseSharingVBPtr() const {
330    assert(CXXInfo && "Record layout does not have C++ specific info!");
331    return CXXInfo->BaseSharingVBPtr;
332  }
333
334  const VBaseOffsetsMapTy &getVBaseOffsetsMap() const {
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
343