path: root/lib/CodeGen/MicrosoftCXXABI.cpp

//===--- 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"; }
  // No known support for deleted functions in MSVC yet, so this choice is
  // arbitrary.
  StringRef GetDeletedVirtualCallName() { return "_purecall"; }

  llvm::Value *adjustToCompleteObject(CodeGenFunction &CGF,
                                      llvm::Value *ptr,
                                      QualType type);

  void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
                                 CXXCtorType Type,
                                 CanQualType &ResTy,
                                 SmallVectorImpl<CanQualType> &ArgTys);

  llvm::BasicBlock *EmitCtorCompleteObjectHandler(CodeGenFunction &CGF);

  void BuildDestructorSignature(const CXXDestructorDecl *Ctor,
                                CXXDtorType Type,
                                CanQualType &ResTy,
                                SmallVectorImpl<CanQualType> &ArgTys);

  void BuildInstanceFunctionParams(CodeGenFunction &CGF,
                                   QualType &ResTy,
                                   FunctionArgList &Params);

  void EmitInstanceFunctionProlog(CodeGenFunction &CGF);

  void EmitConstructorCall(CodeGenFunction &CGF,
                           const CXXConstructorDecl *D,
                           CXXCtorType Type, bool ForVirtualBase,
                           bool Delegating,
                           llvm::Value *This,
                           CallExpr::const_arg_iterator ArgBeg,
                           CallExpr::const_arg_iterator ArgEnd);

  RValue EmitVirtualDestructorCall(CodeGenFunction &CGF,
                                   const CXXDestructorDecl *Dtor,
                                   CXXDtorType DtorType,
                                   SourceLocation CallLoc,
                                   ReturnValueSlot ReturnValue,
                                   llvm::Value *This);

  void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
                       llvm::GlobalVariable *DeclPtr,
                       bool PerformInit);

  // ==== 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);
  static bool needThisReturn(GlobalDecl GD);
};

}

llvm::Value *MicrosoftCXXABI::adjustToCompleteObject(CodeGenFunction &CGF,
                                                     llvm::Value *ptr,
                                                     QualType type) {
  // FIXME: implement
  return ptr;
}

bool MicrosoftCXXABI::needThisReturn(GlobalDecl GD) {
  const CXXMethodDecl* MD = cast<CXXMethodDecl>(GD.getDecl());
  return isa<CXXConstructorDecl>(MD);
}

void MicrosoftCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
                                 CXXCtorType Type,
                                 CanQualType &ResTy,
                                 SmallVectorImpl<CanQualType> &ArgTys) {
  // 'this' is already in place

  // Ctor returns this ptr
  ResTy = ArgTys[0];

  const CXXRecordDecl *Class = Ctor->getParent();
  if (Class->getNumVBases()) {
    // Constructors of classes with virtual bases take an implicit parameter.
    ArgTys.push_back(CGM.getContext().IntTy);
  }
}

llvm::BasicBlock *MicrosoftCXXABI::EmitCtorCompleteObjectHandler(
                                                         CodeGenFunction &CGF) {
  llvm::Value *IsMostDerivedClass = getStructorImplicitParamValue(CGF);
  assert(IsMostDerivedClass &&
         "ctor for a class with virtual bases must have an implicit parameter");
  llvm::Value *IsCompleteObject
    = CGF.Builder.CreateIsNotNull(IsMostDerivedClass, "is_complete_object");

  llvm::BasicBlock *CallVbaseCtorsBB = CGF.createBasicBlock("ctor.init_vbases");
  llvm::BasicBlock *SkipVbaseCtorsBB = CGF.createBasicBlock("ctor.skip_vbases");
  CGF.Builder.CreateCondBr(IsCompleteObject,
                           CallVbaseCtorsBB, SkipVbaseCtorsBB);

  CGF.EmitBlock(CallVbaseCtorsBB);
  // FIXME: emit vbtables somewhere around here.

  // CGF will put the base ctor calls in this basic block for us later.

  return SkipVbaseCtorsBB;
}

void MicrosoftCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
                                               CXXDtorType Type,
                                               CanQualType &ResTy,
                                        SmallVectorImpl<CanQualType> &ArgTys) {
  // 'this' is already in place
  // TODO: 'for base' flag

  if (Type == Dtor_Deleting) {
    // The scalar deleting destructor takes an implicit bool parameter.
    ArgTys.push_back(CGM.getContext().BoolTy);
  }
}

static bool IsDeletingDtor(GlobalDecl GD) {
  const CXXMethodDecl* MD = cast<CXXMethodDecl>(GD.getDecl());
  if (isa<CXXDestructorDecl>(MD)) {
    return GD.getDtorType() == Dtor_Deleting;
  }
  return false;
}

void MicrosoftCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
                                                  QualType &ResTy,
                                                  FunctionArgList &Params) {
  BuildThisParam(CGF, Params);
  if (needThisReturn(CGF.CurGD)) {
    ResTy = Params[0]->getType();
  }

  ASTContext &Context = getContext();
  const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
  if (isa<CXXConstructorDecl>(MD) && MD->getParent()->getNumVBases()) {
    ImplicitParamDecl *IsMostDerived
      = ImplicitParamDecl::Create(Context, 0,
                                  CGF.CurGD.getDecl()->getLocation(),
                                  &Context.Idents.get("is_most_derived"),
                                  Context.IntTy);
    Params.push_back(IsMostDerived);
    getStructorImplicitParamDecl(CGF) = IsMostDerived;
  } else if (IsDeletingDtor(CGF.CurGD)) {
    ImplicitParamDecl *ShouldDelete
      = ImplicitParamDecl::Create(Context, 0,
                                  CGF.CurGD.getDecl()->getLocation(),
                                  &Context.Idents.get("should_call_delete"),
                                  Context.BoolTy);
    Params.push_back(ShouldDelete);
    getStructorImplicitParamDecl(CGF) = ShouldDelete;
  }
}

void MicrosoftCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
  EmitThisParam(CGF);
  if (needThisReturn(CGF.CurGD)) {
    CGF.Builder.CreateStore(getThisValue(CGF), CGF.ReturnValue);
  }

  const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
  if (isa<CXXConstructorDecl>(MD) && MD->getParent()->getNumVBases()) {
    assert(getStructorImplicitParamDecl(CGF) &&
           "no implicit parameter for a constructor with virtual bases?");
    getStructorImplicitParamValue(CGF)
      = CGF.Builder.CreateLoad(
          CGF.GetAddrOfLocalVar(getStructorImplicitParamDecl(CGF)),
          "is_most_derived");
  }

  if (IsDeletingDtor(CGF.CurGD)) {
    assert(getStructorImplicitParamDecl(CGF) &&
           "no implicit parameter for a deleting destructor?");
    getStructorImplicitParamValue(CGF)
      = CGF.Builder.CreateLoad(
          CGF.GetAddrOfLocalVar(getStructorImplicitParamDecl(CGF)),
          "should_call_delete");
  }
}

void MicrosoftCXXABI::EmitConstructorCall(CodeGenFunction &CGF,
                                          const CXXConstructorDecl *D,
                                          CXXCtorType Type, bool ForVirtualBase,
                                          bool Delegating,
                                          llvm::Value *This,
                                          CallExpr::const_arg_iterator ArgBeg,
                                          CallExpr::const_arg_iterator ArgEnd) {
  assert(Type == Ctor_Complete || Type == Ctor_Base);
  llvm::Value *Callee = CGM.GetAddrOfCXXConstructor(D, Ctor_Complete);

  llvm::Value *ImplicitParam = 0;
  QualType ImplicitParamTy