forked from OSchip/llvm-project
203 lines
7.5 KiB
C++
203 lines
7.5 KiB
C++
//===------- MicrosoftCXXABI.cpp - AST support for the Microsoft C++ ABI --===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This provides C++ AST support targeting the Microsoft Visual C++
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// ABI.
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//
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//===----------------------------------------------------------------------===//
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#include "CXXABI.h"
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#include "clang/AST/Attr.h"
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#include "clang/AST/ASTContext.h"
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#include "clang/AST/DeclCXX.h"
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#include "clang/AST/MangleNumberingContext.h"
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#include "clang/AST/RecordLayout.h"
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#include "clang/AST/Type.h"
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#include "clang/Basic/TargetInfo.h"
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using namespace clang;
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namespace {
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/// \brief Numbers things which need to correspond across multiple TUs.
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/// Typically these are things like static locals, lambdas, or blocks.
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class MicrosoftNumberingContext : public MangleNumberingContext {
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unsigned NumStaticLocals;
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public:
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MicrosoftNumberingContext() : NumStaticLocals(0) { }
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/// Static locals are numbered by source order.
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virtual unsigned getManglingNumber(const VarDecl *VD) {
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assert(VD->isStaticLocal());
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return ++NumStaticLocals;
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}
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};
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class MicrosoftCXXABI : public CXXABI {
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ASTContext &Context;
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public:
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MicrosoftCXXABI(ASTContext &Ctx) : Context(Ctx) { }
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std::pair<uint64_t, unsigned>
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getMemberPointerWidthAndAlign(const MemberPointerType *MPT) const;
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CallingConv getDefaultMethodCallConv(bool isVariadic) const {
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if (!isVariadic &&
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Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86)
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return CC_X86ThisCall;
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return CC_C;
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}
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bool isNearlyEmpty(const CXXRecordDecl *RD) const {
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// FIXME: Audit the corners
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if (!RD->isDynamicClass())
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return false;
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const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
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// In the Microsoft ABI, classes can have one or two vtable pointers.
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CharUnits PointerSize =
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Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
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return Layout.getNonVirtualSize() == PointerSize ||
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Layout.getNonVirtualSize() == PointerSize * 2;
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}
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MangleNumberingContext *createMangleNumberingContext() const {
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return new MicrosoftNumberingContext();
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}
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};
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}
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// getNumBases() seems to only give us the number of direct bases, and not the
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// total. This function tells us if we inherit from anybody that uses MI, or if
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// we have a non-primary base class, which uses the multiple inheritance model.
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static bool usesMultipleInheritanceModel(const CXXRecordDecl *RD) {
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while (RD->getNumBases() > 0) {
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if (RD->getNumBases() > 1)
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return true;
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assert(RD->getNumBases() == 1);
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const CXXRecordDecl *Base =
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RD->bases_begin()->getType()->getAsCXXRecordDecl();
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if (RD->isPolymorphic() && !Base->isPolymorphic())
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return true;
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RD = Base;
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}
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return false;
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}
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static MSInheritanceModel MSInheritanceAttrToModel(attr::Kind Kind) {
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switch (Kind) {
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default: llvm_unreachable("expected MS inheritance attribute");
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case attr::SingleInheritance: return MSIM_Single;
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case attr::MultipleInheritance: return MSIM_Multiple;
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case attr::VirtualInheritance: return MSIM_Virtual;
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case attr::UnspecifiedInheritance: return MSIM_Unspecified;
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}
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}
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MSInheritanceModel CXXRecordDecl::getMSInheritanceModel() const {
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if (Attr *IA = this->getAttr<MSInheritanceAttr>())
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return MSInheritanceAttrToModel(IA->getKind());
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// If there was no explicit attribute, the record must be defined already, and
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// we can figure out the inheritance model from its other properties.
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if (this->getNumVBases() > 0)
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return MSIM_Virtual;
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if (usesMultipleInheritanceModel(this))
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return this->isPolymorphic() ? MSIM_MultiplePolymorphic : MSIM_Multiple;
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return this->isPolymorphic() ? MSIM_SinglePolymorphic : MSIM_Single;
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}
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// Returns the number of pointer and integer slots used to represent a member
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// pointer in the MS C++ ABI.
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//
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// Member function pointers have the following general form; however, fields
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// are dropped as permitted (under the MSVC interpretation) by the inheritance
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// model of the actual class.
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//
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// struct {
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// // A pointer to the member function to call. If the member function is
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// // virtual, this will be a thunk that forwards to the appropriate vftable
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// // slot.
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// void *FunctionPointerOrVirtualThunk;
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//
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// // An offset to add to the address of the vbtable pointer after (possibly)
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// // selecting the virtual base but before resolving and calling the function.
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// // Only needed if the class has any virtual bases or bases at a non-zero
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// // offset.
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// int NonVirtualBaseAdjustment;
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//
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// // An offset within the vb-table that selects the virtual base containing
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// // the member. Loading from this offset produces a new offset that is
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// // added to the address of the vb-table pointer to produce the base.
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// int VirtualBaseAdjustmentOffset;
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//
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// // The offset of the vb-table pointer within the object. Only needed for
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// // incomplete types.
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// int VBPtrOffset;
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// };
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static std::pair<unsigned, unsigned>
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getMSMemberPointerSlots(const MemberPointerType *MPT) {
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const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
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MSInheritanceModel Inheritance = RD->getMSInheritanceModel();
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unsigned Ptrs;
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unsigned Ints = 0;
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if (MPT->isMemberFunctionPointer()) {
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// Member function pointers are a struct of a function pointer followed by a
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// variable number of ints depending on the inheritance model used. The
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// function pointer is a real function if it is non-virtual and a vftable
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// slot thunk if it is virtual. The ints select the object base passed for
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// the 'this' pointer.
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Ptrs = 1; // First slot is always a function pointer.
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switch (Inheritance) {
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case MSIM_Unspecified: ++Ints; // VBTableOffset
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case MSIM_Virtual: ++Ints; // VirtualBaseAdjustmentOffset
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case MSIM_MultiplePolymorphic:
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case MSIM_Multiple: ++Ints; // NonVirtualBaseAdjustment
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case MSIM_SinglePolymorphic:
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case MSIM_Single: break; // Nothing
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}
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} else {
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// Data pointers are an aggregate of ints. The first int is an offset
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// followed by vbtable-related offsets.
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Ptrs = 0;
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switch (Inheritance) {
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case MSIM_Unspecified: ++Ints; // VBTableOffset
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case MSIM_Virtual: ++Ints; // VirtualBaseAdjustmentOffset
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case MSIM_MultiplePolymorphic:
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case MSIM_Multiple: // Nothing
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case MSIM_SinglePolymorphic:
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case MSIM_Single: ++Ints; // Field offset
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}
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}
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return std::make_pair(Ptrs, Ints);
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}
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std::pair<uint64_t, unsigned> MicrosoftCXXABI::getMemberPointerWidthAndAlign(
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const MemberPointerType *MPT) const {
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const TargetInfo &Target = Context.getTargetInfo();
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assert(Target.getTriple().getArch() == llvm::Triple::x86 ||
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Target.getTriple().getArch() == llvm::Triple::x86_64);
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unsigned Ptrs, Ints;
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llvm::tie(Ptrs, Ints) = getMSMemberPointerSlots(MPT);
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// The nominal struct is laid out with pointers followed by ints and aligned
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// to a pointer width if any are present and an int width otherwise.
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unsigned PtrSize = Target.getPointerWidth(0);
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unsigned IntSize = Target.getIntWidth();
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uint64_t Width = Ptrs * PtrSize + Ints * IntSize;
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unsigned Align = Ptrs > 0 ? Target.getPointerAlign(0) : Target.getIntAlign();
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Width = llvm::RoundUpToAlignment(Width, Align);
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return std::make_pair(Width, Align);
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}
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CXXABI *clang::CreateMicrosoftCXXABI(ASTContext &Ctx) {
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return new MicrosoftCXXABI(Ctx);
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}
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