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//===------- MicrosoftCXXABI.cpp - AST support for the Microsoft C++ ABI --===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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 {
/// \brief Numbers things which need to correspond across multiple TUs.
/// Typically these are things like static locals, lambdas, or blocks.
class MicrosoftNumberingContext : public MangleNumberingContext {
public:
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;
public:
MicrosoftCXXABI(ASTContext &Ctx) : Context(Ctx) { }
std::pair<uint64_t, unsigned>
getMemberPointerWidthAndAlign(const MemberPointerType *MPT) const override;
CallingConv getDefaultMethodCallConv(bool isVariadic) const override {
if (!isVariadic &&
Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86)
return CC_X86ThisCall;
return CC_C;
}
bool isNearlyEmpty(const CXXRecordDecl *RD) const override {
// FIXME: Audit the corners
if (!RD->isDynamicClass())
return false;
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
// In the Microsoft ABI, classes can have one or two vtable pointers.
CharUnits PointerSize =
Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
return Layout.getNonVirtualSize() == PointerSize ||
Layout.getNonVirtualSize() == PointerSize * 2;
}
MangleNumberingContext *createMangleNumberingContext() const override {
return new 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);
}
std::pair<uint64_t, unsigned> MicrosoftCXXABI::getMemberPointerWidthAndAlign(
const MemberPointerType *MPT) const {
const TargetInfo &Target = Context.getTargetInfo();
assert(Target.getTriple().getArch() == llvm::Triple::x86 ||
Target.getTriple().getArch() == llvm::Triple::x86_64);
unsigned Ptrs, Ints;
std::tie(Ptrs, Ints) = getMSMemberPointerSlots(MPT);
// 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.
unsigned PtrSize = Target.getPointerWidth(0);
unsigned IntSize = Target.getIntWidth();
uint64_t Width = Ptrs * PtrSize + Ints * IntSize;
unsigned Align;
// 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().getArch() == llvm::Triple::x86)
Align = 8 * 8;
else if (Ptrs)
Align = Target.getPointerAlign(0);
else
Align = Target.getIntAlign();
if (Target.getTriple().getArch() == llvm::Triple::x86_64)
Width = llvm::RoundUpToAlignment(Width, Align);
return std::make_pair(Width, Align);
}
CXXABI *clang::CreateMicrosoftCXXABI(ASTContext &Ctx) {
return new MicrosoftCXXABI(Ctx);
}
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