xref: /freebsd/contrib/llvm-project/clang/lib/AST/MicrosoftCXXABI.cpp (revision 13ec1e3155c7e9bf037b12af186351b7fa9b9450) 
1 //===------- MicrosoftCXXABI.cpp - AST support for the Microsoft C++ ABI --===//
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 provides C++ AST support targeting the Microsoft Visual C++
10 // ABI.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "CXXABI.h"
15 #include "clang/AST/ASTContext.h"
16 #include "clang/AST/Attr.h"
17 #include "clang/AST/CXXInheritance.h"
18 #include "clang/AST/DeclCXX.h"
19 #include "clang/AST/Mangle.h"
20 #include "clang/AST/MangleNumberingContext.h"
21 #include "clang/AST/RecordLayout.h"
22 #include "clang/AST/Type.h"
23 #include "clang/Basic/TargetInfo.h"
24 
25 using namespace clang;
26 
27 namespace {
28 
29 /// Numbers things which need to correspond across multiple TUs.
30 /// Typically these are things like static locals, lambdas, or blocks.
31 class MicrosoftNumberingContext : public MangleNumberingContext {
32   llvm::DenseMap<const Type *, unsigned> ManglingNumbers;
33   unsigned LambdaManglingNumber;
34   unsigned StaticLocalNumber;
35   unsigned StaticThreadlocalNumber;
36 
37 public:
38   MicrosoftNumberingContext()
39       : MangleNumberingContext(), LambdaManglingNumber(0),
40         StaticLocalNumber(0), StaticThreadlocalNumber(0) {}
41 
42   unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {
43     return ++LambdaManglingNumber;
44   }
45 
46   unsigned getManglingNumber(const BlockDecl *BD) override {
47     const Type *Ty = nullptr;
48     return ++ManglingNumbers[Ty];
49   }
50 
51   unsigned getStaticLocalNumber(const VarDecl *VD) override {
52     if (VD->getTLSKind())
53       return ++StaticThreadlocalNumber;
54     return ++StaticLocalNumber;
55   }
56 
57   unsigned getManglingNumber(const VarDecl *VD,
58                              unsigned MSLocalManglingNumber) override {
59     return MSLocalManglingNumber;
60   }
61 
62   unsigned getManglingNumber(const TagDecl *TD,
63                              unsigned MSLocalManglingNumber) override {
64     return MSLocalManglingNumber;
65   }
66 };
67 
68 class MSHIPNumberingContext : public MicrosoftNumberingContext {
69   std::unique_ptr<MangleNumberingContext> DeviceCtx;
70 
71 public:
72   MSHIPNumberingContext(MangleContext *DeviceMangler) {
73     DeviceCtx = createItaniumNumberingContext(DeviceMangler);
74   }
75 
76   unsigned getDeviceManglingNumber(const CXXMethodDecl *CallOperator) override {
77     return DeviceCtx->getManglingNumber(CallOperator);
78   }
79 };
80 
81 class MicrosoftCXXABI : public CXXABI {
82   ASTContext &Context;
83   llvm::SmallDenseMap<CXXRecordDecl *, CXXConstructorDecl *> RecordToCopyCtor;
84 
85   llvm::SmallDenseMap<TagDecl *, DeclaratorDecl *>
86       UnnamedTagDeclToDeclaratorDecl;
87   llvm::SmallDenseMap<TagDecl *, TypedefNameDecl *>
88       UnnamedTagDeclToTypedefNameDecl;
89 
90   // MangleContext for device numbering context, which is based on Itanium C++
91   // ABI.
92   std::unique_ptr<MangleContext> DeviceMangler;
93 
94 public:
95   MicrosoftCXXABI(ASTContext &Ctx) : Context(Ctx) {
96     if (Context.getLangOpts().CUDA && Context.getAuxTargetInfo()) {
97       assert(Context.getTargetInfo().getCXXABI().isMicrosoft() &&
98              Context.getAuxTargetInfo()->getCXXABI().isItaniumFamily() &&
99              "Unexpected combination of C++ ABIs.");
100       DeviceMangler.reset(
101           Context.createMangleContext(Context.getAuxTargetInfo()));
102     }
103   }
104 
105   MemberPointerInfo
106   getMemberPointerInfo(const MemberPointerType *MPT) const override;
107 
108   CallingConv getDefaultMethodCallConv(bool isVariadic) const override {
109     if (!isVariadic &&
110         Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86)
111       return CC_X86ThisCall;
112     return Context.getTargetInfo().getDefaultCallingConv();
113   }
114 
115   bool isNearlyEmpty(const CXXRecordDecl *RD) const override {
116     llvm_unreachable("unapplicable to the MS ABI");
117   }
118 
119   const CXXConstructorDecl *
120   getCopyConstructorForExceptionObject(CXXRecordDecl *RD) override {
121     return RecordToCopyCtor[RD];
122   }
123 
124   void
125   addCopyConstructorForExceptionObject(CXXRecordDecl *RD,
126                                        CXXConstructorDecl *CD) override {
127     assert(CD != nullptr);
128     assert(RecordToCopyCtor[RD] == nullptr || RecordToCopyCtor[RD] == CD);
129     RecordToCopyCtor[RD] = CD;
130   }
131 
132   void addTypedefNameForUnnamedTagDecl(TagDecl *TD,
133                                        TypedefNameDecl *DD) override {
134     TD = TD->getCanonicalDecl();
135     DD = DD->getCanonicalDecl();
136     TypedefNameDecl *&I = UnnamedTagDeclToTypedefNameDecl[TD];
137     if (!I)
138       I = DD;
139   }
140 
141   TypedefNameDecl *getTypedefNameForUnnamedTagDecl(const TagDecl *TD) override {
142     return UnnamedTagDeclToTypedefNameDecl.lookup(
143         const_cast<TagDecl *>(TD->getCanonicalDecl()));
144   }
145 
146   void addDeclaratorForUnnamedTagDecl(TagDecl *TD,
147                                       DeclaratorDecl *DD) override {
148     TD = TD->getCanonicalDecl();
149     DD = cast<DeclaratorDecl>(DD->getCanonicalDecl());
150     DeclaratorDecl *&I = UnnamedTagDeclToDeclaratorDecl[TD];
151     if (!I)
152       I = DD;
153   }
154 
155   DeclaratorDecl *getDeclaratorForUnnamedTagDecl(const TagDecl *TD) override {
156     return UnnamedTagDeclToDeclaratorDecl.lookup(
157         const_cast<TagDecl *>(TD->getCanonicalDecl()));
158   }
159 
160   std::unique_ptr<MangleNumberingContext>
161   createMangleNumberingContext() const override {
162     if (Context.getLangOpts().CUDA && Context.getAuxTargetInfo()) {
163       assert(DeviceMangler && "Missing device mangler");
164       return std::make_unique<MSHIPNumberingContext>(DeviceMangler.get());
165     }
166     return std::make_unique<MicrosoftNumberingContext>();
167   }
168 };
169 }
170 
171 // getNumBases() seems to only give us the number of direct bases, and not the
172 // total.  This function tells us if we inherit from anybody that uses MI, or if
173 // we have a non-primary base class, which uses the multiple inheritance model.
174 static bool usesMultipleInheritanceModel(const CXXRecordDecl *RD) {
175   while (RD->getNumBases() > 0) {
176     if (RD->getNumBases() > 1)
177       return true;
178     assert(RD->getNumBases() == 1);
179     const CXXRecordDecl *Base =
180         RD->bases_begin()->getType()->getAsCXXRecordDecl();
181     if (RD->isPolymorphic() && !Base->isPolymorphic())
182       return true;
183     RD = Base;
184   }
185   return false;
186 }
187 
188 MSInheritanceModel CXXRecordDecl::calculateInheritanceModel() const {
189   if (!hasDefinition() || isParsingBaseSpecifiers())
190     return MSInheritanceModel::Unspecified;
191   if (getNumVBases() > 0)
192     return MSInheritanceModel::Virtual;
193   if (usesMultipleInheritanceModel(this))
194     return MSInheritanceModel::Multiple;
195   return MSInheritanceModel::Single;
196 }
197 
198 MSInheritanceModel CXXRecordDecl::getMSInheritanceModel() const {
199   MSInheritanceAttr *IA = getAttr<MSInheritanceAttr>();
200   assert(IA && "Expected MSInheritanceAttr on the CXXRecordDecl!");
201   return IA->getInheritanceModel();
202 }
203 
204 bool CXXRecordDecl::nullFieldOffsetIsZero() const {
205   return !inheritanceModelHasOnlyOneField(/*IsMemberFunction=*/false,
206                                           getMSInheritanceModel()) ||
207          (hasDefinition() && isPolymorphic());
208 }
209 
210 MSVtorDispMode CXXRecordDecl::getMSVtorDispMode() const {
211   if (MSVtorDispAttr *VDA = getAttr<MSVtorDispAttr>())
212     return VDA->getVtorDispMode();
213   return getASTContext().getLangOpts().getVtorDispMode();
214 }
215 
216 // Returns the number of pointer and integer slots used to represent a member
217 // pointer in the MS C++ ABI.
218 //
219 // Member function pointers have the following general form;  however, fields
220 // are dropped as permitted (under the MSVC interpretation) by the inheritance
221 // model of the actual class.
222 //
223 //   struct {
224 //     // A pointer to the member function to call.  If the member function is
225 //     // virtual, this will be a thunk that forwards to the appropriate vftable
226 //     // slot.
227 //     void *FunctionPointerOrVirtualThunk;
228 //
229 //     // An offset to add to the address of the vbtable pointer after
230 //     // (possibly) selecting the virtual base but before resolving and calling
231 //     // the function.
232 //     // Only needed if the class has any virtual bases or bases at a non-zero
233 //     // offset.
234 //     int NonVirtualBaseAdjustment;
235 //
236 //     // The offset of the vb-table pointer within the object.  Only needed for
237 //     // incomplete types.
238 //     int VBPtrOffset;
239 //
240 //     // An offset within the vb-table that selects the virtual base containing
241 //     // the member.  Loading from this offset produces a new offset that is
242 //     // added to the address of the vb-table pointer to produce the base.
243 //     int VirtualBaseAdjustmentOffset;
244 //   };
245 static std::pair<unsigned, unsigned>
246 getMSMemberPointerSlots(const MemberPointerType *MPT) {
247   const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
248   MSInheritanceModel Inheritance = RD->getMSInheritanceModel();
249   unsigned Ptrs = 0;
250   unsigned Ints = 0;
251   if (MPT->isMemberFunctionPointer())
252     Ptrs = 1;
253   else
254     Ints = 1;
255   if (inheritanceModelHasNVOffsetField(MPT->isMemberFunctionPointer(),
256                                           Inheritance))
257     Ints++;
258   if (inheritanceModelHasVBPtrOffsetField(Inheritance))
259     Ints++;
260   if (inheritanceModelHasVBTableOffsetField(Inheritance))
261     Ints++;
262   return std::make_pair(Ptrs, Ints);
263 }
264 
265 CXXABI::MemberPointerInfo MicrosoftCXXABI::getMemberPointerInfo(
266     const MemberPointerType *MPT) const {
267   // The nominal struct is laid out with pointers followed by ints and aligned
268   // to a pointer width if any are present and an int width otherwise.
269   const TargetInfo &Target = Context.getTargetInfo();
270   unsigned PtrSize = Target.getPointerWidth(0);
271   unsigned IntSize = Target.getIntWidth();
272 
273   unsigned Ptrs, Ints;
274   std::tie(Ptrs, Ints) = getMSMemberPointerSlots(MPT);
275   MemberPointerInfo MPI;
276   MPI.HasPadding = false;
277   MPI.Width = Ptrs * PtrSize + Ints * IntSize;
278 
279   // When MSVC does x86_32 record layout, it aligns aggregate member pointers to
280   // 8 bytes.  However, __alignof usually returns 4 for data memptrs and 8 for
281   // function memptrs.
282   if (Ptrs + Ints > 1 && Target.getTriple().isArch32Bit())
283     MPI.Align = 64;
284   else if (Ptrs)
285     MPI.Align = Target.getPointerAlign(0);
286   else
287     MPI.Align = Target.getIntAlign();
288 
289   if (Target.getTriple().isArch64Bit()) {
290     MPI.Width = llvm::alignTo(MPI.Width, MPI.Align);
291     MPI.HasPadding = MPI.Width != (Ptrs * PtrSize + Ints * IntSize);
292   }
293   return MPI;
294 }
295 
296 CXXABI *clang::CreateMicrosoftCXXABI(ASTContext &Ctx) {
297   return new MicrosoftCXXABI(Ctx);
298 }
299