VTableBuilder.h revision 8fb9fb66d415ee40447277f649ecdb12b4964385 
1//===--- VTableBuilder.h - C++ vtable layout builder --------------*- 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 contains code dealing with generation of the layout of virtual tables.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_AST_VTABLEBUILDER_H
15#define LLVM_CLANG_AST_VTABLEBUILDER_H
16
17#include "clang/AST/BaseSubobject.h"
18#include "clang/AST/CXXInheritance.h"
19#include "clang/AST/GlobalDecl.h"
20#include "clang/AST/RecordLayout.h"
21#include "clang/Basic/ABI.h"
22#include "llvm/ADT/SetVector.h"
23#include <utility>
24
25namespace clang {
26  class CXXRecordDecl;
27
28/// VTableComponent - Represents a single component in a vtable.
29class VTableComponent {
30public:
31  enum Kind {
32    CK_VCallOffset,
33    CK_VBaseOffset,
34    CK_OffsetToTop,
35    CK_RTTI,
36    CK_FunctionPointer,
37
38    /// CK_CompleteDtorPointer - A pointer to the complete destructor.
39    CK_CompleteDtorPointer,
40
41    /// CK_DeletingDtorPointer - A pointer to the deleting destructor.
42    CK_DeletingDtorPointer,
43
44    /// CK_UnusedFunctionPointer - In some cases, a vtable function pointer
45    /// will end up never being called. Such vtable function pointers are
46    /// represented as a CK_UnusedFunctionPointer.
47    CK_UnusedFunctionPointer
48  };
49
50  VTableComponent() { }
51
52  static VTableComponent MakeVCallOffset(CharUnits Offset) {
53    return VTableComponent(CK_VCallOffset, Offset);
54  }
55
56  static VTableComponent MakeVBaseOffset(CharUnits Offset) {
57    return VTableComponent(CK_VBaseOffset, Offset);
58  }
59
60  static VTableComponent MakeOffsetToTop(CharUnits Offset) {
61    return VTableComponent(CK_OffsetToTop, Offset);
62  }
63
64  static VTableComponent MakeRTTI(const CXXRecordDecl *RD) {
65    return VTableComponent(CK_RTTI, reinterpret_cast<uintptr_t>(RD));
66  }
67
68  static VTableComponent MakeFunction(const CXXMethodDecl *MD) {
69    assert(!isa<CXXDestructorDecl>(MD) &&
70           "Don't use MakeFunction with destructors!");
71
72    return VTableComponent(CK_FunctionPointer,
73                           reinterpret_cast<uintptr_t>(MD));
74  }
75
76  static VTableComponent MakeCompleteDtor(const CXXDestructorDecl *DD) {
77    return VTableComponent(CK_CompleteDtorPointer,
78                           reinterpret_cast<uintptr_t>(DD));
79  }
80
81  static VTableComponent MakeDeletingDtor(const CXXDestructorDecl *DD) {
82    return VTableComponent(CK_DeletingDtorPointer,
83                           reinterpret_cast<uintptr_t>(DD));
84  }
85
86  static VTableComponent MakeUnusedFunction(const CXXMethodDecl *MD) {
87    assert(!isa<CXXDestructorDecl>(MD) &&
88           "Don't use MakeUnusedFunction with destructors!");
89    return VTableComponent(CK_UnusedFunctionPointer,
90                           reinterpret_cast<uintptr_t>(MD));
91  }
92
93  static VTableComponent getFromOpaqueInteger(uint64_t I) {
94    return VTableComponent(I);
95  }
96
97  /// getKind - Get the kind of this vtable component.
98  Kind getKind() const {
99    return (Kind)(Value & 0x7);
100  }
101
102  CharUnits getVCallOffset() const {
103    assert(getKind() == CK_VCallOffset && "Invalid component kind!");
104
105    return getOffset();
106  }
107
108  CharUnits getVBaseOffset() const {
109    assert(getKind() == CK_VBaseOffset && "Invalid component kind!");
110
111    return getOffset();
112  }
113
114  CharUnits getOffsetToTop() const {
115    assert(getKind() == CK_OffsetToTop && "Invalid component kind!");
116
117    return getOffset();
118  }
119
120  const CXXRecordDecl *getRTTIDecl() const {
121    assert(getKind() == CK_RTTI && "Invalid component kind!");
122
123    return reinterpret_cast<CXXRecordDecl *>(getPointer());
124  }
125
126  const CXXMethodDecl *getFunctionDecl() const {
127    assert(getKind() == CK_FunctionPointer);
128
129    return reinterpret_cast<CXXMethodDecl *>(getPointer());
130  }
131
132  const CXXDestructorDecl *getDestructorDecl() const {
133    assert((getKind() == CK_CompleteDtorPointer ||
134            getKind() == CK_DeletingDtorPointer) && "Invalid component kind!");
135
136    return reinterpret_cast<CXXDestructorDecl *>(getPointer());
137  }
138
139  const CXXMethodDecl *getUnusedFunctionDecl() const {
140    assert(getKind() == CK_UnusedFunctionPointer);
141
142    return reinterpret_cast<CXXMethodDecl *>(getPointer());
143  }
144
145private:
146  VTableComponent(Kind ComponentKind, CharUnits Offset) {
147    assert((ComponentKind == CK_VCallOffset ||
148            ComponentKind == CK_VBaseOffset ||
149            ComponentKind == CK_OffsetToTop) && "Invalid component kind!");
150    assert(Offset.getQuantity() <= ((1LL << 56) - 1) && "Offset is too big!");
151
152    Value = ((Offset.getQuantity() << 3) | ComponentKind);
153  }
154
155  VTableComponent(Kind ComponentKind, uintptr_t Ptr) {
156    assert((ComponentKind == CK_RTTI ||
157            ComponentKind == CK_FunctionPointer ||
158            ComponentKind == CK_CompleteDtorPointer ||
159            ComponentKind == CK_DeletingDtorPointer ||
160            ComponentKind == CK_UnusedFunctionPointer) &&
161            "Invalid component kind!");
162
163    assert((Ptr & 7) == 0 && "Pointer not sufficiently aligned!");
164
165    Value = Ptr | ComponentKind;
166  }
167
168  CharUnits getOffset() const {
169    assert((getKind() == CK_VCallOffset || getKind() == CK_VBaseOffset ||
170            getKind() == CK_OffsetToTop) && "Invalid component kind!");
171
172    return CharUnits::fromQuantity(Value >> 3);
173  }
174
175  uintptr_t getPointer() const {
176    assert((getKind() == CK_RTTI ||
177            getKind() == CK_FunctionPointer ||
178            getKind() == CK_CompleteDtorPointer ||
179            getKind() == CK_DeletingDtorPointer ||
180            getKind() == CK_UnusedFunctionPointer) &&
181           "Invalid component kind!");
182
183    return static_cast<uintptr_t>(Value & ~7ULL);
184  }
185
186  explicit VTableComponent(uint64_t Value)
187    : Value(Value) { }
188
189  /// The kind is stored in the lower 3 bits of the value. For offsets, we
190  /// make use of the facts that classes can't be larger than 2^55 bytes,
191  /// so we store the offset in the lower part of the 61 bytes that remain.
192  /// (The reason that we're not simply using a PointerIntPair here is that we
193  /// need the offsets to be 64-bit, even when on a 32-bit machine).
194  int64_t Value;
195};
196
197class VTableLayout {
198public:
199  typedef std::pair<uint64_t, ThunkInfo> VTableThunkTy;
200  typedef SmallVector<ThunkInfo, 1> ThunkInfoVectorTy;
201
202  typedef const VTableComponent *vtable_component_iterator;
203  typedef const VTableThunkTy *vtable_thunk_iterator;
204
205  typedef llvm::DenseMap<BaseSubobject, uint64_t> AddressPointsMapTy;
206private:
207  uint64_t NumVTableComponents;
208  llvm::OwningArrayPtr<VTableComponent> VTableComponents;
209
210  /// VTableThunks - Contains thunks needed by vtables.
211  uint64_t NumVTableThunks;
212  llvm::OwningArrayPtr<VTableThunkTy> VTableThunks;
213
214  /// Address points - Address points for all vtables.
215  AddressPointsMapTy AddressPoints;
216
217public:
218  VTableLayout(uint64_t NumVTableComponents,
219               const VTableComponent *VTableComponents,
220               uint64_t NumVTableThunks,
221               const VTableThunkTy *VTableThunks,
222               const AddressPointsMapTy &AddressPoints);
223  ~VTableLayout();
224
225  uint64_t getNumVTableComponents() const {
226    return NumVTableComponents;
227  }
228
229  vtable_component_iterator vtable_component_begin() const {
230   return VTableComponents.get();
231  }
232
233  vtable_component_iterator vtable_component_end() const {
234   return VTableComponents.get()+NumVTableComponents;
235  }
236
237  uint64_t getNumVTableThunks() const {
238    return NumVTableThunks;
239  }
240
241  vtable_thunk_iterator vtable_thunk_begin() const {
242   return VTableThunks.get();
243  }
244
245  vtable_thunk_iterator vtable_thunk_end() const {
246   return VTableThunks.get()+NumVTableThunks;
247  }
248
249  uint64_t getAddressPoint(BaseSubobject Base) const {
250    assert(AddressPoints.count(Base) &&
251           "Did not find address point!");
252
253    uint64_t AddressPoint = AddressPoints.lookup(Base);
254    assert(AddressPoint && "Address point must not be zero!");
255
256    return AddressPoint;
257  }
258
259  const AddressPointsMapTy &getAddressPoints() const {
260    return AddressPoints;
261  }
262};
263
264class VTableContext {
265  ASTContext &Context;
266
267public:
268  typedef SmallVector<std::pair<uint64_t, ThunkInfo>, 1>
269    VTableThunksTy;
270  typedef SmallVector<ThunkInfo, 1> ThunkInfoVectorTy;
271
272private:
273  /// MethodVTableIndices - Contains the index (relative to the vtable address
274  /// point) where the function pointer for a virtual function is stored.
275  typedef llvm::DenseMap<GlobalDecl, int64_t> MethodVTableIndicesTy;
276  MethodVTableIndicesTy MethodVTableIndices;
277
278  typedef llvm::DenseMap<const CXXRecordDecl *, const VTableLayout *>
279    VTableLayoutMapTy;
280  VTableLayoutMapTy VTableLayouts;
281
282  /// NumVirtualFunctionPointers - Contains the number of virtual function
283  /// pointers in the vtable for a given record decl.
284  llvm::DenseMap<const CXXRecordDecl *, uint64_t> NumVirtualFunctionPointers;
285
286  typedef std::pair<const CXXRecordDecl *,
287                    const CXXRecordDecl *> ClassPairTy;
288
289  /// VirtualBaseClassOffsetOffsets - Contains the vtable offset (relative to
290  /// the address point) in chars where the offsets for virtual bases of a class
291  /// are stored.
292  typedef llvm::DenseMap<ClassPairTy, CharUnits>
293    VirtualBaseClassOffsetOffsetsMapTy;
294  VirtualBaseClassOffsetOffsetsMapTy VirtualBaseClassOffsetOffsets;
295
296  typedef llvm::DenseMap<const CXXMethodDecl *, ThunkInfoVectorTy> ThunksMapTy;
297
298  /// Thunks - Contains all thunks that a given method decl will need.
299  ThunksMapTy Thunks;
300
301  void ComputeMethodVTableIndices(const CXXRecordDecl *RD);
302
303  /// ComputeVTableRelatedInformation - Compute and store all vtable related
304  /// information (vtable layout, vbase offset offsets, thunks etc) for the
305  /// given record decl.
306  void ComputeVTableRelatedInformation(const CXXRecordDecl *RD);
307
308public:
309  VTableContext(ASTContext &Context) : Context(Context) {}
310  ~VTableContext();
311
312  const VTableLayout &getVTableLayout(const CXXRecordDecl *RD) {
313    ComputeVTableRelatedInformation(RD);
314    assert(VTableLayouts.count(RD) && "No layout for this record decl!");
315
316    return *VTableLayouts[RD];
317  }
318
319  VTableLayout *
320  createConstructionVTableLayout(const CXXRecordDecl *MostDerivedClass,
321                                 CharUnits MostDerivedClassOffset,
322                                 bool MostDerivedClassIsVirtual,
323                                 const CXXRecordDecl *LayoutClass);
324
325  const ThunkInfoVectorTy *getThunkInfo(const CXXMethodDecl *MD) {
326    ComputeVTableRelatedInformation(MD->getParent());
327
328    ThunksMapTy::const_iterator I = Thunks.find(MD);
329    if (I == Thunks.end()) {
330      // We did not find a thunk for this method.
331      return 0;
332    }
333
334    return &I->second;
335  }
336
337  /// getNumVirtualFunctionPointers - Return the number of virtual function
338  /// pointers in the vtable for a given record decl.
339  uint64_t getNumVirtualFunctionPointers(const CXXRecordDecl *RD);
340
341  /// getMethodVTableIndex - Return the index (relative to the vtable address
342  /// point) where the function pointer for the given virtual function is
343  /// stored.
344  uint64_t getMethodVTableIndex(GlobalDecl GD);
345
346  /// getVirtualBaseOffsetOffset - Return the offset in chars (relative to the
347  /// vtable address point) where the offset of the virtual base that contains
348  /// the given base is stored, otherwise, if no virtual base contains the given
349  /// class, return 0.  Base must be a virtual base class or an unambigious
350  /// base.
351  CharUnits getVirtualBaseOffsetOffset(const CXXRecordDecl *RD,
352                                       const CXXRecordDecl *VBase);
353};
354
355}
356
357#endif
358