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| //===------- MicrosoftCXXABI.cpp - AST support for the Microsoft C++ ABI --===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This provides C++ AST support targeting the Microsoft Visual C++
// ABI.
//
//===----------------------------------------------------------------------===//
#include "CXXABI.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/MangleNumberingContext.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/Type.h"
#include "clang/Basic/TargetInfo.h"
using namespace clang;
namespace {
/// Numbers things which need to correspond across multiple TUs.
/// Typically these are things like static locals, lambdas, or blocks.
class MicrosoftNumberingContext : public MangleNumberingContext {
llvm::DenseMap<const Type *, unsigned> ManglingNumbers;
unsigned LambdaManglingNumber;
unsigned StaticLocalNumber;
unsigned StaticThreadlocalNumber;
public:
MicrosoftNumberingContext()
: MangleNumberingContext(), LambdaManglingNumber(0),
StaticLocalNumber(0), StaticThreadlocalNumber(0) {}
unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {
return ++LambdaManglingNumber;
}
unsigned getManglingNumber(const BlockDecl *BD) override {
const Type *Ty = nullptr;
return ++ManglingNumbers[Ty];
}
unsigned getStaticLocalNumber(const VarDecl *VD) override {
if (VD->getTLSKind())
return ++StaticThreadlocalNumber;
return ++StaticLocalNumber;
}
unsigned getManglingNumber(const VarDecl *VD,
unsigned MSLocalManglingNumber) override {
return MSLocalManglingNumber;
}
unsigned getManglingNumber(const TagDecl *TD,
unsigned MSLocalManglingNumber) override {
return MSLocalManglingNumber;
}
};
class MicrosoftCXXABI : public CXXABI {
ASTContext &Context;
llvm::SmallDenseMap<CXXRecordDecl *, CXXConstructorDecl *> RecordToCopyCtor;
llvm::SmallDenseMap<TagDecl *, DeclaratorDecl *>
UnnamedTagDeclToDeclaratorDecl;
llvm::SmallDenseMap<TagDecl *, TypedefNameDecl *>
UnnamedTagDeclToTypedefNameDecl;
public:
MicrosoftCXXABI(ASTContext &Ctx) : Context(Ctx) { }
MemberPointerInfo
getMemberPointerInfo(const MemberPointerType *MPT) const override;
CallingConv getDefaultMethodCallConv(bool isVariadic) const override {
if (!isVariadic &&
Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86)
return CC_X86ThisCall;
return Context.getTargetInfo().getDefaultCallingConv();
}
bool isNearlyEmpty(const CXXRecordDecl *RD) const override {
llvm_unreachable("unapplicable to the MS ABI");
}
const CXXConstructorDecl *
getCopyConstructorForExceptionObject(CXXRecordDecl *RD) override {
return RecordToCopyCtor[RD];
}
void
addCopyConstructorForExceptionObject(CXXRecordDecl *RD,
CXXConstructorDecl *CD) override {
assert(CD != nullptr);
assert(RecordToCopyCtor[RD] == nullptr || RecordToCopyCtor[RD] == CD);
RecordToCopyCtor[RD] = CD;
}
void addTypedefNameForUnnamedTagDecl(TagDecl *TD,
TypedefNameDecl *DD) override {
TD = TD->getCanonicalDecl();
DD = DD->getCanonicalDecl();
TypedefNameDecl *&I = UnnamedTagDeclToTypedefNameDecl[TD];
if (!I)
I = DD;
}
TypedefNameDecl *getTypedefNameForUnnamedTagDecl(const TagDecl *TD) override {
return UnnamedTagDeclToTypedefNameDecl.lookup(
const_cast<TagDecl *>(TD->getCanonicalDecl()));
}
void addDeclaratorForUnnamedTagDecl(TagDecl *TD,
DeclaratorDecl *DD) override {
TD = TD->getCanonicalDecl();
DD = cast<DeclaratorDecl>(DD->getCanonicalDecl());
DeclaratorDecl *&I = UnnamedTagDeclToDeclaratorDecl[TD];
if (!I)
I = DD;
}
DeclaratorDecl *getDeclaratorForUnnamedTagDecl(const TagDecl *TD) override {
return UnnamedTagDeclToDeclaratorDecl.lookup(
const_cast<TagDecl *>(TD->getCanonicalDecl()));
}
std::unique_ptr<MangleNumberingContext>
createMangleNumberingContext() const override {
return std::make_unique<MicrosoftNumberingContext>();
}
};
}
// getNumBases() seems to only give us the number of direct bases, and not the
// total. This function tells us if we inherit from anybody that uses MI, or if
// we have a non-primary base class, which uses the multiple inheritance model.
static bool usesMultipleInheritanceModel(const CXXRecordDecl *RD) {
while (RD->getNumBases() > 0) {
if (RD->getNumBases() > 1)
return true;
assert(RD->getNumBases() == 1);
const CXXRecordDecl *Base =
RD->bases_begin()->getType()->getAsCXXRecordDecl();
if (RD->isPolymorphic() && !Base->isPolymorphic())
return true;
RD = Base;
}
return false;
}
MSInheritanceAttr::Spelling CXXRecordDecl::calculateInheritanceModel() const {
if (!hasDefinition() || isParsingBaseSpecifiers())
return MSInheritanceAttr::Keyword_unspecified_inheritance;
if (getNumVBases() > 0)
return MSInheritanceAttr::Keyword_virtual_inheritance;
if (usesMultipleInheritanceModel(this))
return MSInheritanceAttr::Keyword_multiple_inheritance;
return MSInheritanceAttr::Keyword_single_inheritance;
}
MSInheritanceAttr::Spelling
CXXRecordDecl::getMSInheritanceModel() const {
MSInheritanceAttr *IA = getAttr<MSInheritanceAttr>();
assert(IA && "Expected MSInheritanceAttr on the CXXRecordDecl!");
return IA->getSemanticSpelling();
}
MSVtorDispAttr::Mode CXXRecordDecl::getMSVtorDispMode() const {
if (MSVtorDispAttr *VDA = getAttr<MSVtorDispAttr>())
return VDA->getVtorDispMode();
return MSVtorDispAttr::Mode(getASTContext().getLangOpts().VtorDispMode);
}
// Returns the number of pointer and integer slots used to represent a member
// pointer in the MS C++ ABI.
//
// Member function pointers have the following general form; however, fields
// are dropped as permitted (under the MSVC interpretation) by the inheritance
// model of the actual class.
//
// struct {
// // A pointer to the member function to call. If the member function is
// // virtual, this will be a thunk that forwards to the appropriate vftable
// // slot.
// void *FunctionPointerOrVirtualThunk;
//
// // An offset to add to the address of the vbtable pointer after
// // (possibly) selecting the virtual base but before resolving and calling
// // the function.
// // Only needed if the class has any virtual bases or bases at a non-zero
// // offset.
// int NonVirtualBaseAdjustment;
//
// // The offset of the vb-table pointer within the object. Only needed for
// // incomplete types.
// int VBPtrOffset;
//
// // An offset within the vb-table that selects the virtual base containing
// // the member. Loading from this offset produces a new offset that is
// // added to the address of the vb-table pointer to produce the base.
// int VirtualBaseAdjustmentOffset;
// };
static std::pair<unsigned, unsigned>
getMSMemberPointerSlots(const MemberPointerType *MPT) {
const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
MSInheritanceAttr::Spelling Inheritance = RD->getMSInheritanceModel();
unsigned Ptrs = 0;
unsigned Ints = 0;
if (MPT->isMemberFunctionPointer())
Ptrs = 1;
else
Ints = 1;
if (MSInheritanceAttr::hasNVOffsetField(MPT->isMemberFunctionPointer(),
Inheritance))
Ints++;
if (MSInheritanceAttr::hasVBPtrOffsetField(Inheritance))
Ints++;
if (MSInheritanceAttr::hasVBTableOffsetField(Inheritance))
Ints++;
return std::make_pair(Ptrs, Ints);
}
CXXABI::MemberPointerInfo MicrosoftCXXABI::getMemberPointerInfo(
const MemberPointerType *MPT) const {
// The nominal struct is laid out with pointers followed by ints and aligned
// to a pointer width if any are present and an int width otherwise.
const TargetInfo &Target = Context.getTargetInfo();
unsigned PtrSize = Target.getPointerWidth(0);
unsigned IntSize = Target.getIntWidth();
unsigned Ptrs, Ints;
std::tie(Ptrs, Ints) = getMSMemberPointerSlots(MPT);
MemberPointerInfo MPI;
MPI.HasPadding = false;
MPI.Width = Ptrs * PtrSize + Ints * IntSize;
// When MSVC does x86_32 record layout, it aligns aggregate member pointers to
// 8 bytes. However, __alignof usually returns 4 for data memptrs and 8 for
// function memptrs.
if (Ptrs + Ints > 1 && Target.getTriple().isArch32Bit())
MPI.Align = 64;
else if (Ptrs)
MPI.Align = Target.getPointerAlign(0);
else
MPI.Align = Target.getIntAlign();
if (Target.getTriple().isArch64Bit()) {
MPI.Width = llvm::alignTo(MPI.Width, MPI.Align);
MPI.HasPadding = MPI.Width != (Ptrs * PtrSize + Ints * IntSize);
}
return MPI;
}
CXXABI *clang::CreateMicrosoftCXXABI(ASTContext &Ctx) {
return new MicrosoftCXXABI(Ctx);
}
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