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