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270 lines
9.1 KiB
270 lines
9.1 KiB
//===------- MicrosoftCXXABI.cpp - AST support for the Microsoft C++ ABI --===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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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/ASTContext.h"
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#include "clang/AST/Attr.h"
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#include "clang/AST/CXXInheritance.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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/// 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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llvm::DenseMap<const Type *, unsigned> ManglingNumbers;
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unsigned LambdaManglingNumber;
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unsigned StaticLocalNumber;
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unsigned StaticThreadlocalNumber;
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public:
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MicrosoftNumberingContext()
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: MangleNumberingContext(), LambdaManglingNumber(0),
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StaticLocalNumber(0), StaticThreadlocalNumber(0) {}
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unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {
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return ++LambdaManglingNumber;
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}
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unsigned getManglingNumber(const BlockDecl *BD) override {
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const Type *Ty = nullptr;
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return ++ManglingNumbers[Ty];
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}
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unsigned getStaticLocalNumber(const VarDecl *VD) override {
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if (VD->getTLSKind())
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return ++StaticThreadlocalNumber;
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return ++StaticLocalNumber;
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}
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unsigned getManglingNumber(const VarDecl *VD,
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unsigned MSLocalManglingNumber) override {
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return MSLocalManglingNumber;
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}
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unsigned getManglingNumber(const TagDecl *TD,
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unsigned MSLocalManglingNumber) override {
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return MSLocalManglingNumber;
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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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llvm::SmallDenseMap<CXXRecordDecl *, CXXConstructorDecl *> RecordToCopyCtor;
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llvm::SmallDenseMap<TagDecl *, DeclaratorDecl *>
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UnnamedTagDeclToDeclaratorDecl;
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llvm::SmallDenseMap<TagDecl *, TypedefNameDecl *>
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UnnamedTagDeclToTypedefNameDecl;
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public:
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MicrosoftCXXABI(ASTContext &Ctx) : Context(Ctx) { }
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MemberPointerInfo
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getMemberPointerInfo(const MemberPointerType *MPT) const override;
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CallingConv getDefaultMethodCallConv(bool isVariadic) const override {
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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 Context.getTargetInfo().getDefaultCallingConv();
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}
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bool isNearlyEmpty(const CXXRecordDecl *RD) const override {
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llvm_unreachable("unapplicable to the MS ABI");
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}
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const CXXConstructorDecl *
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getCopyConstructorForExceptionObject(CXXRecordDecl *RD) override {
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return RecordToCopyCtor[RD];
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}
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void
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addCopyConstructorForExceptionObject(CXXRecordDecl *RD,
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CXXConstructorDecl *CD) override {
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assert(CD != nullptr);
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assert(RecordToCopyCtor[RD] == nullptr || RecordToCopyCtor[RD] == CD);
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RecordToCopyCtor[RD] = CD;
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}
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void addTypedefNameForUnnamedTagDecl(TagDecl *TD,
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TypedefNameDecl *DD) override {
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TD = TD->getCanonicalDecl();
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DD = DD->getCanonicalDecl();
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TypedefNameDecl *&I = UnnamedTagDeclToTypedefNameDecl[TD];
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if (!I)
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I = DD;
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}
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TypedefNameDecl *getTypedefNameForUnnamedTagDecl(const TagDecl *TD) override {
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return UnnamedTagDeclToTypedefNameDecl.lookup(
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const_cast<TagDecl *>(TD->getCanonicalDecl()));
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}
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void addDeclaratorForUnnamedTagDecl(TagDecl *TD,
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DeclaratorDecl *DD) override {
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TD = TD->getCanonicalDecl();
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DD = cast<DeclaratorDecl>(DD->getCanonicalDecl());
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DeclaratorDecl *&I = UnnamedTagDeclToDeclaratorDecl[TD];
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if (!I)
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I = DD;
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}
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DeclaratorDecl *getDeclaratorForUnnamedTagDecl(const TagDecl *TD) override {
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return UnnamedTagDeclToDeclaratorDecl.lookup(
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const_cast<TagDecl *>(TD->getCanonicalDecl()));
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}
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std::unique_ptr<MangleNumberingContext>
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createMangleNumberingContext() const override {
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return std::make_unique<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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MSInheritanceModel CXXRecordDecl::calculateInheritanceModel() const {
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if (!hasDefinition() || isParsingBaseSpecifiers())
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return MSInheritanceModel::Unspecified;
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if (getNumVBases() > 0)
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return MSInheritanceModel::Virtual;
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if (usesMultipleInheritanceModel(this))
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return MSInheritanceModel::Multiple;
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return MSInheritanceModel::Single;
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}
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MSInheritanceModel CXXRecordDecl::getMSInheritanceModel() const {
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MSInheritanceAttr *IA = getAttr<MSInheritanceAttr>();
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assert(IA && "Expected MSInheritanceAttr on the CXXRecordDecl!");
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return IA->getInheritanceModel();
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}
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bool CXXRecordDecl::nullFieldOffsetIsZero() const {
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return !inheritanceModelHasOnlyOneField(/*IsMemberFunction=*/false,
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getMSInheritanceModel()) ||
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(hasDefinition() && isPolymorphic());
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}
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MSVtorDispMode CXXRecordDecl::getMSVtorDispMode() const {
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if (MSVtorDispAttr *VDA = getAttr<MSVtorDispAttr>())
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return VDA->getVtorDispMode();
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return getASTContext().getLangOpts().getVtorDispMode();
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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
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// // (possibly) selecting the virtual base but before resolving and calling
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// // 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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// // 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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// // 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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static std::pair<unsigned, unsigned>
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getMSMemberPointerSlots(const MemberPointerType *MPT) {
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const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
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MSInheritanceModel Inheritance = RD->getMSInheritanceModel();
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unsigned Ptrs = 0;
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unsigned Ints = 0;
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if (MPT->isMemberFunctionPointer())
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Ptrs = 1;
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else
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Ints = 1;
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if (inheritanceModelHasNVOffsetField(MPT->isMemberFunctionPointer(),
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Inheritance))
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Ints++;
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if (inheritanceModelHasVBPtrOffsetField(Inheritance))
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Ints++;
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if (inheritanceModelHasVBTableOffsetField(Inheritance))
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Ints++;
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return std::make_pair(Ptrs, Ints);
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}
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CXXABI::MemberPointerInfo MicrosoftCXXABI::getMemberPointerInfo(
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const MemberPointerType *MPT) const {
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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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const TargetInfo &Target = Context.getTargetInfo();
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unsigned PtrSize = Target.getPointerWidth(0);
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unsigned IntSize = Target.getIntWidth();
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unsigned Ptrs, Ints;
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std::tie(Ptrs, Ints) = getMSMemberPointerSlots(MPT);
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MemberPointerInfo MPI;
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MPI.HasPadding = false;
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MPI.Width = Ptrs * PtrSize + Ints * IntSize;
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// When MSVC does x86_32 record layout, it aligns aggregate member pointers to
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// 8 bytes. However, __alignof usually returns 4 for data memptrs and 8 for
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// function memptrs.
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if (Ptrs + Ints > 1 && Target.getTriple().isArch32Bit())
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MPI.Align = 64;
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else if (Ptrs)
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MPI.Align = Target.getPointerAlign(0);
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else
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MPI.Align = Target.getIntAlign();
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if (Target.getTriple().isArch64Bit()) {
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MPI.Width = llvm::alignTo(MPI.Width, MPI.Align);
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MPI.HasPadding = MPI.Width != (Ptrs * PtrSize + Ints * IntSize);
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}
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return MPI;
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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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