1 //===------- MicrosoftCXXABI.cpp - AST support for the Microsoft C++ ABI --===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This provides C++ AST support targeting the Microsoft Visual C++
13 //===----------------------------------------------------------------------===//
16 #include "clang/AST/Attr.h"
17 #include "clang/AST/ASTContext.h"
18 #include "clang/AST/DeclCXX.h"
19 #include "clang/AST/MangleNumberingContext.h"
20 #include "clang/AST/RecordLayout.h"
21 #include "clang/AST/Type.h"
22 #include "clang/Basic/TargetInfo.h"
24 using namespace clang;
28 /// \brief Numbers things which need to correspond across multiple TUs.
29 /// Typically these are things like static locals, lambdas, or blocks.
30 class MicrosoftNumberingContext : public MangleNumberingContext {
31 unsigned NumStaticLocals;
34 MicrosoftNumberingContext() : NumStaticLocals(0) { }
36 /// Static locals are numbered by source order.
37 virtual unsigned getManglingNumber(const VarDecl *VD) {
38 assert(VD->isStaticLocal());
39 return ++NumStaticLocals;
43 class MicrosoftCXXABI : public CXXABI {
46 MicrosoftCXXABI(ASTContext &Ctx) : Context(Ctx) { }
48 std::pair<uint64_t, unsigned>
49 getMemberPointerWidthAndAlign(const MemberPointerType *MPT) const;
51 CallingConv getDefaultMethodCallConv(bool isVariadic) const {
53 Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86)
54 return CC_X86ThisCall;
58 bool isNearlyEmpty(const CXXRecordDecl *RD) const {
59 // FIXME: Audit the corners
60 if (!RD->isDynamicClass())
63 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
65 // In the Microsoft ABI, classes can have one or two vtable pointers.
66 CharUnits PointerSize =
67 Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
68 return Layout.getNonVirtualSize() == PointerSize ||
69 Layout.getNonVirtualSize() == PointerSize * 2;
72 MangleNumberingContext *createMangleNumberingContext() const {
73 return new MicrosoftNumberingContext();
78 // getNumBases() seems to only give us the number of direct bases, and not the
79 // total. This function tells us if we inherit from anybody that uses MI, or if
80 // we have a non-primary base class, which uses the multiple inheritance model.
81 static bool usesMultipleInheritanceModel(const CXXRecordDecl *RD) {
82 while (RD->getNumBases() > 0) {
83 if (RD->getNumBases() > 1)
85 assert(RD->getNumBases() == 1);
86 const CXXRecordDecl *Base =
87 RD->bases_begin()->getType()->getAsCXXRecordDecl();
88 if (RD->isPolymorphic() && !Base->isPolymorphic())
95 static MSInheritanceModel MSInheritanceAttrToModel(attr::Kind Kind) {
97 default: llvm_unreachable("expected MS inheritance attribute");
98 case attr::SingleInheritance: return MSIM_Single;
99 case attr::MultipleInheritance: return MSIM_Multiple;
100 case attr::VirtualInheritance: return MSIM_Virtual;
101 case attr::UnspecifiedInheritance: return MSIM_Unspecified;
105 MSInheritanceModel CXXRecordDecl::getMSInheritanceModel() const {
106 if (Attr *IA = this->getAttr<MSInheritanceAttr>())
107 return MSInheritanceAttrToModel(IA->getKind());
108 // If there was no explicit attribute, the record must be defined already, and
109 // we can figure out the inheritance model from its other properties.
110 if (this->getNumVBases() > 0)
112 if (usesMultipleInheritanceModel(this))
113 return this->isPolymorphic() ? MSIM_MultiplePolymorphic : MSIM_Multiple;
114 return this->isPolymorphic() ? MSIM_SinglePolymorphic : MSIM_Single;
117 // Returns the number of pointer and integer slots used to represent a member
118 // pointer in the MS C++ ABI.
120 // Member function pointers have the following general form; however, fields
121 // are dropped as permitted (under the MSVC interpretation) by the inheritance
122 // model of the actual class.
125 // // A pointer to the member function to call. If the member function is
126 // // virtual, this will be a thunk that forwards to the appropriate vftable
128 // void *FunctionPointerOrVirtualThunk;
130 // // An offset to add to the address of the vbtable pointer after (possibly)
131 // // selecting the virtual base but before resolving and calling the function.
132 // // Only needed if the class has any virtual bases or bases at a non-zero
134 // int NonVirtualBaseAdjustment;
136 // // An offset within the vb-table that selects the virtual base containing
137 // // the member. Loading from this offset produces a new offset that is
138 // // added to the address of the vb-table pointer to produce the base.
139 // int VirtualBaseAdjustmentOffset;
141 // // The offset of the vb-table pointer within the object. Only needed for
142 // // incomplete types.
145 static std::pair<unsigned, unsigned>
146 getMSMemberPointerSlots(const MemberPointerType *MPT) {
147 const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
148 MSInheritanceModel Inheritance = RD->getMSInheritanceModel();
151 if (MPT->isMemberFunctionPointer()) {
152 // Member function pointers are a struct of a function pointer followed by a
153 // variable number of ints depending on the inheritance model used. The
154 // function pointer is a real function if it is non-virtual and a vftable
155 // slot thunk if it is virtual. The ints select the object base passed for
156 // the 'this' pointer.
157 Ptrs = 1; // First slot is always a function pointer.
158 switch (Inheritance) {
159 case MSIM_Unspecified: ++Ints; // VBTableOffset
160 case MSIM_Virtual: ++Ints; // VirtualBaseAdjustmentOffset
161 case MSIM_MultiplePolymorphic:
162 case MSIM_Multiple: ++Ints; // NonVirtualBaseAdjustment
163 case MSIM_SinglePolymorphic:
164 case MSIM_Single: break; // Nothing
167 // Data pointers are an aggregate of ints. The first int is an offset
168 // followed by vbtable-related offsets.
170 switch (Inheritance) {
171 case MSIM_Unspecified: ++Ints; // VBTableOffset
172 case MSIM_Virtual: ++Ints; // VirtualBaseAdjustmentOffset
173 case MSIM_MultiplePolymorphic:
174 case MSIM_Multiple: // Nothing
175 case MSIM_SinglePolymorphic:
176 case MSIM_Single: ++Ints; // Field offset
179 return std::make_pair(Ptrs, Ints);
182 std::pair<uint64_t, unsigned> MicrosoftCXXABI::getMemberPointerWidthAndAlign(
183 const MemberPointerType *MPT) const {
184 const TargetInfo &Target = Context.getTargetInfo();
185 assert(Target.getTriple().getArch() == llvm::Triple::x86 ||
186 Target.getTriple().getArch() == llvm::Triple::x86_64);
188 llvm::tie(Ptrs, Ints) = getMSMemberPointerSlots(MPT);
189 // The nominal struct is laid out with pointers followed by ints and aligned
190 // to a pointer width if any are present and an int width otherwise.
191 unsigned PtrSize = Target.getPointerWidth(0);
192 unsigned IntSize = Target.getIntWidth();
193 uint64_t Width = Ptrs * PtrSize + Ints * IntSize;
194 unsigned Align = Ptrs > 0 ? Target.getPointerAlign(0) : Target.getIntAlign();
195 Width = llvm::RoundUpToAlignment(Width, Align);
196 return std::make_pair(Width, Align);
199 CXXABI *clang::CreateMicrosoftCXXABI(ASTContext &Ctx) {
200 return new MicrosoftCXXABI(Ctx);