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//===--- MicrosoftCXXABI.cpp - Emit LLVM Code from ASTs for a Module ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This provides C++ code generation targeting the Microsoft Visual C++ ABI.
// The class in this file generates structures that follow the Microsoft
// Visual C++ ABI, which is actually not very well documented at all outside
// of Microsoft.
//
//===----------------------------------------------------------------------===//
#include "CGCXXABI.h"
#include "CodeGenModule.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
using namespace clang;
using namespace CodeGen;
namespace {
class MicrosoftCXXABI : public CGCXXABI {
public:
MicrosoftCXXABI(CodeGenModule &CGM) : CGCXXABI(CGM) {}
StringRef GetPureVirtualCallName() { return "_purecall"; }
void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
CXXCtorType Type,
CanQualType &ResTy,
SmallVectorImpl<CanQualType> &ArgTys) {
// 'this' is already in place
// TODO: 'for base' flag
}
void BuildDestructorSignature(const CXXDestructorDecl *Ctor,
CXXDtorType Type,
CanQualType &ResTy,
SmallVectorImpl<CanQualType> &ArgTys) {
// 'this' is already in place
// TODO: 'for base' flag
}
void BuildInstanceFunctionParams(CodeGenFunction &CGF,
QualType &ResTy,
FunctionArgList &Params) {
BuildThisParam(CGF, Params);
// TODO: 'for base' flag
}
void EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
EmitThisParam(CGF);
// TODO: 'for base' flag
}
void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
llvm::GlobalVariable *DeclPtr,
bool PerformInit);
void EmitVTables(const CXXRecordDecl *Class);
// ==== Notes on array cookies =========
//
// MSVC seems to only use cookies when the class has a destructor; a
// two-argument usual array deallocation function isn't sufficient.
//
// For example, this code prints "100" and "1":
// struct A {
// char x;
// void *operator new[](size_t sz) {
// printf("%u\n", sz);
// return malloc(sz);
// }
// void operator delete[](void *p, size_t sz) {
// printf("%u\n", sz);
// free(p);
// }
// };
// int main() {
// A *p = new A[100];
// delete[] p;
// }
// Whereas it prints "104" and "104" if you give A a destructor.
bool requiresArrayCookie(const CXXDeleteExpr *expr, QualType elementType);
bool requiresArrayCookie(const CXXNewExpr *expr);
CharUnits getArrayCookieSizeImpl(QualType type);
llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
llvm::Value *NewPtr,
llvm::Value *NumElements,
const CXXNewExpr *expr,
QualType ElementType);
llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF,
llvm::Value *allocPtr,
CharUnits cookieSize);
};
}
bool MicrosoftCXXABI::requiresArrayCookie(const CXXDeleteExpr *expr,
QualType elementType) {
// Microsoft seems to completely ignore the possibility of a
// two-argument usual deallocation function.
return elementType.isDestructedType();
}
bool MicrosoftCXXABI::requiresArrayCookie(const CXXNewExpr *expr) {
// Microsoft seems to completely ignore the possibility of a
// two-argument usual deallocation function.
return expr->getAllocatedType().isDestructedType();
}
CharUnits MicrosoftCXXABI::getArrayCookieSizeImpl(QualType type) {
// The array cookie is always a size_t; we then pad that out to the
// alignment of the element type.
ASTContext &Ctx = getContext();
return std::max(Ctx.getTypeSizeInChars(Ctx.getSizeType()),
Ctx.getTypeAlignInChars(type));
}
llvm::Value *MicrosoftCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
llvm::Value *allocPtr,
CharUnits cookieSize) {
unsigned AS = cast<llvm::PointerType>(allocPtr->getType())->getAddressSpace();
llvm::Value *numElementsPtr =
CGF.Builder.CreateBitCast(allocPtr, CGF.SizeTy->getPointerTo(AS));
return CGF.Builder.CreateLoad(numElementsPtr);
}
llvm::Value* MicrosoftCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
llvm::Value *newPtr,
llvm::Value *numElements,
const CXXNewExpr *expr,
QualType elementType) {
assert(requiresArrayCookie(expr));
// The size of the cookie.
CharUnits cookieSize = getArrayCookieSizeImpl(elementType);
// Compute an offset to the cookie.
llvm::Value *cookiePtr = newPtr;
// Write the number of elements into the appropriate slot.
unsigned AS = cast<llvm::PointerType>(newPtr->getType())->getAddressSpace();
llvm::Value *numElementsPtr
= CGF.Builder.CreateBitCast(cookiePtr, CGF.SizeTy->getPointerTo(AS));
CGF.Builder.CreateStore(numElements, numElementsPtr);
// Finally, compute a pointer to the actual data buffer by skipping
// over the cookie completely.
return CGF.Builder.CreateConstInBoundsGEP1_64(newPtr,
cookieSize.getQuantity());
}
void MicrosoftCXXABI::EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
llvm::GlobalVariable *DeclPtr,
bool PerformInit) {
// FIXME: this code was only tested for global initialization.
// Not sure whether we want thread-safe static local variables as VS
// doesn't make them thread-safe.
// Emit the initializer and add a global destructor if appropriate.
CGF.EmitCXXGlobalVarDeclInit(D, DeclPtr, PerformInit);
}
void MicrosoftCXXABI::EmitVTables(const CXXRecordDecl *Class) {
// FIXME: implement
}
CGCXXABI *clang::CodeGen::CreateMicrosoftCXXABI(CodeGenModule &CGM) {
return new MicrosoftCXXABI(CGM);
}
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