CGClass.cpp

//===--- CGClass.cpp - Emit LLVM Code for C++ classes ---------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This contains code dealing with C++ code generation of classes
//
//===----------------------------------------------------------------------===//

#include "CodeGenFunction.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/StmtCXX.h"

using namespace clang;
using namespace CodeGen;

static uint64_t 
ComputeNonVirtualBaseClassOffset(ASTContext &Context, 
                                 const CXXRecordDecl *DerivedClass,
                                 CXXBaseSpecifierArray::iterator Start,
                                 CXXBaseSpecifierArray::iterator End) {
  uint64_t Offset = 0;
  
  const CXXRecordDecl *RD = DerivedClass;
  
  for (CXXBaseSpecifierArray::iterator I = Start; I != End; ++I) {
    const CXXBaseSpecifier *Base = *I;
    assert(!Base->isVirtual() && "Should not see virtual bases here!");

    // Get the layout.
    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
    
    const CXXRecordDecl *BaseDecl = 
      cast<CXXRecordDecl>(Base->getType()->getAs<RecordType>()->getDecl());
    
    // Add the offset.
    Offset += Layout.getBaseClassOffset(BaseDecl);
    
    RD = BaseDecl;
  }
  
  // FIXME: We should not use / 8 here.
  return Offset / 8;
}
                                 
static uint64_t 
ComputeNonVirtualBaseClassOffset(ASTContext &Context,
                                 const CXXBasePath &Path,
                                 unsigned Start) {
  uint64_t Offset = 0;

  for (unsigned i = Start, e = Path.size(); i != e; ++i) {
    const CXXBasePathElement& Element = Path[i];

    // Get the layout.
    const ASTRecordLayout &Layout = Context.getASTRecordLayout(Element.Class);
    
    const CXXBaseSpecifier *BS = Element.Base;
    assert(!BS->isVirtual() && "Should not see virtual bases here!");
    
    const CXXRecordDecl *Base = 
      cast<CXXRecordDecl>(BS->getType()->getAs<RecordType>()->getDecl());
    
    // Add the offset.
    Offset += Layout.getBaseClassOffset(Base) / 8;
  }

  return Offset;
}

llvm::Constant *
CodeGenModule::GetNonVirtualBaseClassOffset(const CXXRecordDecl *ClassDecl,
                                        const CXXBaseSpecifierArray &BasePath) {
  assert(!BasePath.empty() && "Base path should not be empty!");

  uint64_t Offset = 
    ComputeNonVirtualBaseClassOffset(getContext(), ClassDecl, 
                                     BasePath.begin(), BasePath.end());
  if (!Offset)
    return 0;
  
  const llvm::Type *PtrDiffTy = 
  Types.ConvertType(getContext().getPointerDiffType());
  
  return llvm::ConstantInt::get(PtrDiffTy, Offset);
}

/// Gets the address of a virtual base class within a complete object.
/// This should only be used for (1) non-virtual bases or (2) virtual bases
/// when the type is known to be complete (e.g. in complete destructors).
///
/// The object pointed to by 'This' is assumed to be non-null.
llvm::Value *
CodeGenFunction::GetAddressOfBaseOfCompleteClass(llvm::Value *This,
                                                 bool isBaseVirtual,
                                                 const CXXRecordDecl *Derived,
                                                 const CXXRecordDecl *Base) {
  // 'this' must be a pointer (in some address space) to Derived.
  assert(This->getType()->isPointerTy() &&
         cast<llvm::PointerType>(This->getType())->getElementType()
           == ConvertType(Derived));

  // Compute the offset of the virtual base.
  uint64_t Offset;
  const ASTRecordLayout &Layout = getContext().getASTRecordLayout(Derived);
  if (isBaseVirtual)
    Offset = Layout.getVBaseClassOffset(Base);
  else
    Offset = Layout.getBaseClassOffset(Base);

  // Shift and cast down to the base type.
  // TODO: for complete types, this should be possible with a GEP.
  llvm::Value *V = This;
  if (Offset) {
    const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(getLLVMContext());
    V = Builder.CreateBitCast(V, Int8PtrTy);
    V = Builder.CreateConstInBoundsGEP1_64(V, Offset / 8);
  }
  V = Builder.CreateBitCast(V, ConvertType(Base)->getPointerTo());

  return V;
}

static llvm::Value *
ApplyNonVirtualAndVirtualOffset(CodeGenFunction &CGF, llvm::Value *ThisPtr,
                                uint64_t NonVirtual, llvm::Value *Virtual) {
  const llvm::Type *PtrDiffTy = 
    CGF.ConvertType(CGF.getContext().getPointerDiffType());
  
  llvm::Value *NonVirtualOffset = 0;
  if (NonVirtual)
    NonVirtualOffset = llvm::ConstantInt::get(PtrDiffTy, NonVirtual);
  
  llvm::Value *BaseOffset;
  if (Virtual) {
    if (NonVirtualOffset)
      BaseOffset = CGF.Builder.CreateAdd(Virtual, NonVirtualOffset);
    else
      BaseOffset = Virtual;
  } else
    BaseOffset = NonVirtualOffset;
  
  // Apply the base offset.
  const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
  ThisPtr = CGF.Builder.CreateBitCast(ThisPtr, Int8PtrTy);
  ThisPtr = CGF.Builder.CreateGEP(ThisPtr, BaseOffset, "add.ptr");

  return ThisPtr;
}

llvm::Value *
CodeGenFunction::GetAddressOfBaseClass(llvm::Value *Value, 
                                       const CXXRecordDecl *ClassDecl,
                                       const CXXBaseSpecifierArray &BasePath, 
                                       bool NullCheckValue) {
  assert(!BasePath.empty() && "Base path should not be empty!");

  CXXBaseSpecifierArray::iterator Start = BasePath.begin();
  const CXXRecordDecl *VBase = 0;
  
  // Get the virtual base.
  if ((*Start)->isVirtual()) {
    VBase = 
      cast<CXXRecordDecl>((*Start)->getType()->getAs<RecordType>()->getDecl());
    ++Start;
  }
  
  uint64_t NonVirtualOffset = 
    ComputeNonVirtualBaseClassOffset(getContext(), VBase ? VBase : ClassDecl,
                                     Start, BasePath.end());

  // Get the base pointer type.
  const llvm::Type *BasePtrTy = 
    ConvertType((BasePath.end()[-1])->getType())->getPointerTo();
  
  if (!NonVirtualOffset && !VBase) {
    // Just cast back.
    return Builder.CreateBitCast(Value, BasePtrTy);
  }    
  
  llvm::BasicBlock *CastNull = 0;
  llvm::BasicBlock *CastNotNull = 0;
  llvm::BasicBlock *CastEnd = 0;
  
  if (NullCheckValue) {
    CastNull = createBasicBlock("cast.null");
    CastNotNull = createBasicBlock("cast.notnull");
    CastEnd = createBasicBlock("cast.end");
    
    llvm::Value *IsNull = 
      Builder.CreateICmpEQ(Value,
                           llvm::Constant::getNullValue(Value->getType()));
    Builder.CreateCondBr(IsNull, CastNull, CastNotNull);
    EmitBlock(CastNotNull);
  }

  llvm::Value *VirtualOffset = 0;

  if (VBase)
    VirtualOffset = GetVirtualBaseClassOffset(Value, ClassDecl, VBase);

  // Apply the offsets.
  Value = ApplyNonVirtualAndVirtualOffset(*this, Value, NonVirtualOffset, 
                                          VirtualOffset);
  
  // Cast back.
  Value = Builder.CreateBitCast(Value, BasePtrTy);
 
  if (NullCheckValue) {
    Builder.CreateBr(CastEnd);
    EmitBlock(CastNull);
    Builder.CreateBr(CastEnd);
    EmitBlock(CastEnd);
    
    llvm::PHINode *PHI = Builder.CreatePHI(Value->getType());
    PHI->reserveOperandSpace(2);
    PHI->addIncoming(Value, CastNotNull);
    PHI->addIncoming(llvm::Constant::getNullValue(Value->getType()), 
                     CastNull);
    Value = PHI;
  }
  
  return Value;
}

llvm::Value *
CodeGenFunction::OldGetAddressOfBaseClass(llvm::Value *Value,
                                          const CXXRecordDecl *Class,
                                          const CXXRecordDecl *BaseClass) {
  QualType BTy =
    getContext().getCanonicalType(
      getContext().getTypeDeclType(BaseClass));
  const llvm::Type *BasePtrTy = llvm::PointerType::getUnqual(ConvertType(BTy));

  if (Class == BaseClass) {
    // Just cast back.
    return Builder.CreateBitCast(Value, BasePtrTy);
  }

#ifndef NDEBUG
  CXXBasePaths Paths(/*FindAmbiguities=*/true,
                     /*RecordPaths=*/true, /*DetectVirtual=*/false);
#else
  CXXBasePaths Paths(/*FindAmbiguities=*/false,
                     /*RecordPaths=*/true, /*DetectVirtual=*/false);
#endif
  if (!const_cast<CXXRecordDecl *>(Class)->
        isDerivedFrom(const_cast<CXXRecordDecl *>(BaseClass), Paths)) {
    assert(false && "Class must be derived from the passed in base class!");
    return 0;
  }

#if 0
  // FIXME: Re-enable this assert when the underlying bugs have been fixed.
  assert(!Paths.isAmbiguous(BTy) && "Path is ambiguous");
#endif

  unsigned Start = 0;

  const CXXBasePath &Path = Paths.front();
  const CXXRecordDecl *VBase = 0;
  for (unsigned i = 0, e = Path.size(); i != e; ++i) {
    const CXXBasePathElement& Element = Path[i];
    if (Element.Base->isVirtual()) {
      Start = i+1;
      QualType VBaseType = Element.Base->getType();
      VBase = cast<CXXRecordDecl>(VBaseType->getAs<RecordType>()->getDecl());
    }
  }

  uint64_t Offset = 
    ComputeNonVirtualBaseClassOffset(getContext(), Paths.front(), Start);
  
  if (!Offset && !VBase) {
    // Just cast back.
    return Builder.CreateBitCast(Value, BasePtrTy);
  }    

  llvm::Value *VirtualOffset = 0;

  if (VBase)
    VirtualOffset = GetVirtualBaseClassOffset(Value, Class, VBase);

  // Apply the offsets.
  Value = ApplyNonVirtualAndVirtualOffset(*this, Value, Offset, VirtualOffset);
  
  // Cast back.
  Value = Builder.CreateBitCast(Value, BasePtrTy);
  return Value;
}

llvm::Value *
CodeGenFunction::GetAddressOfDerivedClass(llvm::Value *Value,
                                          const CXXRecordDecl *DerivedClass,
                                          const CXXBaseSpecifierArray &BasePath,
                                          bool NullCheckValue) {
  assert(!BasePath.empty() && "Base path should not be empty!");

  QualType DerivedTy =
    getContext().getCanonicalType(
    getContext().getTypeDeclType(const_cast<CXXRecordDecl*>(DerivedClass)));
  const llvm::Type *DerivedPtrTy = ConvertType(DerivedTy)->getPointerTo();
  
  llvm::Value *NonVirtualOffset =
    CGM.GetNonVirtualBaseClassOffset(DerivedClass, BasePath);
  
  if (!NonVirtualOffset) {
    // No offset, we can just cast back.
    return Builder.CreateBitCast(Value, DerivedPtrTy);
  }
  
  llvm::BasicBlock *CastNull = 0;
  llvm::BasicBlock *CastNotNull = 0;
  llvm::BasicBlock *CastEnd = 0;
  
  if (NullCheckValue) {
    CastNull = createBasicBlock("cast.null");
    CastNotNull = createBasicBlock("cast.notnull");
    CastEnd = createBasicBlock("cast.end");
    
    llvm::Value *IsNull = 
    Builder.CreateICmpEQ(Value,
                         llvm::Constant::getNullValue(Value->getType()));
    Builder.CreateCondBr(IsNull, CastNull, CastNotNull);
    EmitBlock(CastNotNull);
  }
  
  // Apply the offset.
  Value = Builder.CreatePtrToInt(Value, NonVirtualOffset->getType());
  Value = Builder.CreateSub(Value, NonVirtualOffset);
  Value = Builder.CreateIntToPtr(Value, DerivedPtrTy);

  // Just cast.
  Value = Builder.CreateBitCast(Value, DerivedPtrTy);

  if (NullCheckValue) {
    Builder.CreateBr(CastEnd);
    EmitBlock(CastNull);
    Builder.CreateBr(CastEnd);
    EmitBlock(CastEnd);
    
    llvm::PHINode *PHI = Builder.CreatePHI(Value->getType());
    PHI->reserveOperandSpace(2);
    PHI->addIncoming(Value, CastNotNull);
    PHI->addIncoming(llvm::Constant::getNullValue(Value->getType()), 
                     CastNull);
    Value = PHI;
  }
  
  return Value;
}

/// EmitCopyCtorCall - Emit a call to a copy constructor.
static void
EmitCopyCtorCall(CodeGenFunction &CGF,
                 const CXXConstructorDecl *CopyCtor, CXXCtorType CopyCtorType,
                 llvm::Value *ThisPtr, llvm::Value *VTT, llvm::Value *Src) {
  llvm::Value *Callee = CGF.CGM.GetAddrOfCXXConstructor(CopyCtor, CopyCtorType);

  CallArgList CallArgs;

  // Push the this ptr.
  CallArgs.push_back(std::make_pair(RValue::get(ThisPtr),
                                    CopyCtor->getThisType(CGF.getContext())));
  
  // Push the VTT parameter if necessary.
  if (VTT) {
    QualType T = CGF.getContext().getPointerType(CGF.getContext().VoidPtrTy);
    CallArgs.push_back(std::make_pair(RValue::get(VTT), T));
  }
 
  // Push the Src ptr.
  CallArgs.push_back(std::make_pair(RValue::get(Src),
                                    CopyCtor->getParamDecl(0)->getType()));


  {
    CodeGenFunction::CXXTemporariesCleanupScope Scope(CGF);

    // If the copy constructor has default arguments, emit them.
    for (unsigned I = 1, E = CopyCtor->getNumParams(); I < E; ++I) {
      const ParmVarDecl *Param = CopyCtor->getParamDecl(I);
      const Expr *DefaultArgExpr = Param->getDefaultArg();

      assert(DefaultArgExpr && "Ctor parameter must have default arg!");

      QualType ArgType = Param->getType();
      CallArgs.push_back(std::make_pair(CGF.EmitCallArg(DefaultArgExpr, 
                                                        ArgType),
                                        ArgType));
    }

    const FunctionProtoType *FPT =
      CopyCtor->getType()->getAs<FunctionProtoType>();
    CGF.EmitCall(CGF.CGM.getTypes().getFunctionInfo(CallArgs, FPT),
                 Callee, ReturnValueSlot(), CallArgs, CopyCtor);
  }
}
                             
/// EmitClassAggrMemberwiseCopy - This routine generates code to copy a class
/// array of objects from SrcValue to DestValue. Copying can be either a bitwise
/// copy or via a copy constructor call.
//  FIXME. Consolidate this with EmitCXXAggrConstructorCall.
void
CodeGenFunction::EmitClassAggrMemberwiseCopy(llvm::Value *Dest,
                                             llvm::Value *Src,
                                             const ConstantArrayType *Array,
                                             const CXXRecordDecl *ClassDecl) {
  // Create a temporary for the loop index and initialize it with 0.
  llvm::Value *IndexPtr = CreateTempAlloca(llvm::Type::getInt64Ty(VMContext),
                                           "loop.index");
  llvm::Value* zeroConstant =
    llvm::Constant::getNullValue(llvm::Type::getInt64Ty(VMContext));
  Builder.CreateStore(zeroConstant, IndexPtr);
  // Start the loop with a block that tests the condition.
  llvm::BasicBlock *CondBlock = createBasicBlock("for.cond");
  llvm::BasicBlock *AfterFor = createBasicBlock("for.end");

  EmitBlock(CondBlock);

  llvm::BasicBlock *ForBody = createBasicBlock("for.body");
  // Generate: if (loop-index < number-of-elements fall to the loop body,
  // otherwise, go to the block after the for-loop.
  uint64_t NumElements = getContext().getConstantArrayElementCount(Array);
  llvm::Value * NumElementsPtr =
    llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), NumElements);
  llvm::Value *Counter = Builder.CreateLoad(IndexPtr);
  llvm::Value *IsLess = Builder.CreateICmpULT(Counter, NumElementsPtr,
                                              "isless");
  // If the condition is true, execute the body.
  Builder.CreateCondBr(IsLess, ForBody, AfterFor);

  EmitBlock(ForBody);
  llvm::BasicBlock *ContinueBlock = createBasicBlock("for.inc");
  
  // Inside the loop body, emit the constructor call on the array element.
  Counter = Builder.CreateLoad(IndexPtr);
  Dest = Builder.CreateInBoundsGEP(Dest, Counter, "destaddress");
  Src = Builder.CreateInBoundsGEP(Src, Counter, "srcaddress");
  EmitClassMemberwiseCopy(Dest, Src, ClassDecl);

  EmitBlock(ContinueBlock);

  // Emit the increment of the loop counter.
  llvm::Value *NextVal = llvm::ConstantInt::get(Counter->getType(), 1);
  Counter = Builder.CreateLoad(IndexPtr);
  NextVal = Builder.CreateAdd(Counter, NextVal, "inc");
  Builder.CreateStore(NextVal, IndexPtr);

  // Finally, branch back up to the condition for the next iteration.
  EmitBranch(CondBlock);

  // Emit the fall-through block.
  EmitBlock(AfterFor, true);
}

/// EmitClassAggrCopyAssignment - This routine generates code to assign a class
/// array of objects from SrcValue to DestValue. Assignment can be either a
/// bitwise assignment or via a copy assignment operator function call.
/// FIXME. This can be consolidated with EmitClassAggrMemberwiseCopy
void CodeGenFunction::EmitClassAggrCopyAssignment(llvm::Value *Dest,
                                            llvm::Value *Src,
                                            const ConstantArrayType *Array,
                                            const CXXRecordDecl *BaseClassDecl,
                                            QualType Ty) {
  bool BitwiseAssign = BaseClassDecl->hasTrivialCopyAssignment();

  // Create a temporary for the loop index and initialize it with 0.
  llvm::Value *IndexPtr = CreateTempAlloca(llvm::Type::getInt64Ty(VMContext),
                                           "loop.index");
  llvm::Value* zeroConstant =
    llvm::Constant::getNullValue(llvm::Type::getInt64Ty(VMContext));
  Builder.CreateStore(zeroConstant, IndexPtr);
  
  // Start the loop with a block that tests the condition.
  llvm::BasicBlock *CondBlock = createBasicBlock("for.cond");
  llvm::BasicBlock *AfterFor = createBasicBlock("for.end");

  EmitBlock(CondBlock);

  llvm::BasicBlock *ForBody = createBasicBlock("for.body");
  // Generate: if (loop-index < number-of-elements fall to the loop body,
  // otherwise, go to the block after the for-loop.
  uint64_t NumElements = getContext().getConstantArrayElementCount(Array);
  llvm::Value * NumElementsPtr =
    llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), NumElements);
  llvm::Value *Counter = Builder.CreateLoad(IndexPtr);
  llvm::Value *IsLess = Builder.CreateICmpULT(Counter, NumElementsPtr,
                                              "isless");
  // If the condition is true, execute the body.
  Builder.CreateCondBr(IsLess, ForBody, AfterFor);

  EmitBlock(ForBody);
  llvm::BasicBlock *ContinueBlock = createBasicBlock("for.inc");
  // Inside the loop body, emit the assignment operator call on array element.
  Counter = Builder.CreateLoad(IndexPtr);
  Src = Builder.CreateInBoundsGEP(Src, Counter, "srcaddress");
  Dest = Builder.CreateInBoundsGEP(Dest, Counter, "destaddress");
  const CXXMethodDecl *MD = 0;
  if (BitwiseAssign)
    EmitAggregateCopy(Dest, Src, Ty);
  else {
    BaseClassDecl->hasConstCopyAssignment(getContext(), MD);
    assert(MD && "EmitClassAggrCopyAssignment - No user assign");
    const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
    const llvm::Type *LTy =
    CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(MD),
                                   FPT->isVariadic());
    llvm::Constant *Callee = CGM.GetAddrOfFunction(MD, LTy);

    CallArgList CallArgs;
    // Push the this (Dest) ptr.
    CallArgs.push_back(std::make_pair(RValue::get(Dest),
                                      MD->getThisType(getContext())));

    // Push the Src ptr.
    QualType SrcTy = MD->getParamDecl(0)->getType();
    RValue SrcValue = SrcTy->isReferenceType() ? RValue::get(Src) :
                                                 RValue::getAggregate(Src);
    CallArgs.push_back(std::make_pair(SrcValue, SrcTy));
    EmitCall(CGM.getTypes().getFunctionInfo(CallArgs, FPT),
             Callee, ReturnValueSlot(), CallArgs, MD);
  }
  EmitBlock(ContinueBlock);

  // Emit the increment of the loop counter.
  llvm::Value *NextVal = llvm::ConstantInt::get(Counter->getType(), 1);
  Counter = Builder.CreateLoad(IndexPtr);
  NextVal = Builder.CreateAdd(Counter, NextVal, "inc");
  Builder.CreateStore(NextVal, IndexPtr);

  // Finally, branch back up to the condition for the next iteration.
  EmitBranch(CondBlock);

  // Emit the fall-through block.
  EmitBlock(AfterFor, true);
}

/// GetVTTParameter - Return the VTT parameter that should be passed to a
/// base constructor/destructor with virtual bases.
static llvm::Value *GetVTTParameter(CodeGenFunction &CGF, GlobalDecl GD) {
  if (!CodeGenVTables::needsVTTParameter(GD)) {
    // This constructor/destructor does not need a VTT parameter.
    return 0;
  }
  
  const CXXRecordDecl *RD = cast<CXXMethodDecl>(CGF.CurFuncDecl)->getParent();
  const CXXRecordDecl *Base = cast<CXXMethodDecl>(GD.getDecl())->getParent();

  llvm::Value *VTT;

  uint64_t SubVTTIndex;

  // If the record matches the base, this is the complete ctor/dtor
  // variant calling the base variant in a class with virtual bases.
  if (RD == Base) {
    assert(!CodeGenVTables::needsVTTParameter(CGF.CurGD) &&
           "doing no-op VTT offset in base dtor/ctor?");
    SubVTTIndex = 0;
  } else {
    SubVTTIndex = CGF.CGM.getVTables().getSubVTTIndex(RD, Base);
    assert(SubVTTIndex != 0 && "Sub-VTT index must be greater than zero!");
  }
  
  if (CodeGenVTables::needsVTTParameter(CGF.CurGD)) {
    // A VTT parameter was passed to the constructor, use it.
    VTT = CGF.LoadCXXVTT();
    VTT = CGF.Builder.CreateConstInBoundsGEP1_64(VTT, SubVTTIndex);
  } else {
    // We're the complete constructor, so get the VTT by name.
    VTT = CGF.CGM.getVTables().getVTT(RD);
    VTT = CGF.Builder.CreateConstInBoundsGEP2_64(VTT, 0, SubVTTIndex);
  }

  return VTT;
}

                                    
/// EmitClassMemberwiseCopy - This routine generates code to copy a class
/// object from SrcValue to DestValue.
void CodeGenFunction::EmitClassMemberwiseCopy(llvm::Value *Dest, 
                                              llvm::Value *Src,
                                              const CXXRecordDecl *ClassDecl) {
  if (ClassDecl->hasTrivialCopyConstructor()) {
    EmitAggregateCopy(Dest, Src, getContext().getTagDeclType(ClassDecl));
    return;
  }

  // FIXME: Does this get the right copy constructor?
  const CXXConstructorDecl *CopyConstructor = 
    ClassDecl->getCopyConstructor(getContext(), 0);
  assert(CopyConstructor && "Did not find copy constructor!");
  
  EmitCopyCtorCall(*this, CopyConstructor, Ctor_Complete, Dest, 0, Src);
}

/// EmitClassCopyAssignment - This routine generates code to copy assign a class
/// object from SrcValue to DestValue. Assignment can be either a bitwise
/// assignment of via an assignment operator call.
// FIXME. Consolidate this with EmitClassMemberwiseCopy as they share a lot.
void CodeGenFunction::EmitClassCopyAssignment(
                                        llvm::Value *Dest, llvm::Value *Src,
                                        const CXXRecordDecl *ClassDecl,
                                        const CXXRecordDecl *BaseClassDecl,
                                        QualType Ty) {
  if (ClassDecl) {
    Dest = OldGetAddressOfBaseClass(Dest, ClassDecl, BaseClassDecl);
    Src = OldGetAddressOfBaseClass(Src, ClassDecl, BaseClassDecl);
  }
  if (BaseClassDecl->hasTrivialCopyAssignment()) {
    EmitAggregateCopy(Dest, Src, Ty);
    return;
  }

  const CXXMethodDecl *MD = 0;
  BaseClassDecl->hasConstCopyAssignment(getContext(), MD);
  assert(MD && "EmitClassCopyAssignment - missing copy assign");

  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
  const llvm::Type *LTy =
    CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(MD),
                                   FPT->isVariadic());
  llvm::Constant *Callee = CGM.GetAddrOfFunction(MD, LTy);

  CallArgList CallArgs;
  // Push the this (Dest) ptr.
  CallArgs.push_back(std::make_pair(RValue::get(Dest),
                                    MD->getThisType(getContext())));

  // Push the Src ptr.
  QualType SrcTy = MD->getParamDecl(0)->getType();
  RValue SrcValue = SrcTy->isReferenceType() ? RValue::get(Src) :
                                               RValue::getAggregate(Src);
  CallArgs.push_back(std::make_pair(SrcValue, SrcTy));
  EmitCall(CGM.getTypes().getFunctionInfo(CallArgs, FPT),
           Callee, ReturnValueSlot(), CallArgs, MD);
}

/// SynthesizeCXXCopyConstructor - This routine implicitly defines body of a
/// copy constructor, in accordance with section 12.8 (p7 and p8) of C++03
/// The implicitly-defined copy constructor for class X performs a memberwise
/// copy of its subobjects. The order of copying is the same as the order of
/// initialization of bases and members in a user-defined constructor
/// Each subobject is copied in the manner appropriate to its type:
///  if the subobject is of class type, the copy constructor for the class is
///  used;
///  if the subobject is an array, each element is copied, in the manner
///  appropriate to the element type;
///  if the subobject is of scalar type, the built-in assignment operator is
///  used.
/// Virtual base class subobjects shall be copied only once by the
/// implicitly-defined copy constructor

void 
CodeGenFunction::SynthesizeCXXCopyConstructor(const FunctionArgList &Args) {
  const CXXConstructorDecl *Ctor = cast<CXXConstructorDecl>(CurGD.getDecl());
  const CXXRecordDecl *ClassDecl = Ctor->getParent();
  assert(!ClassDecl->hasUserDeclaredCopyConstructor() &&
      "SynthesizeCXXCopyConstructor - copy constructor has definition already");
  assert(!Ctor->isTrivial() && "shouldn't need to generate trivial ctor");

  FunctionArgList::const_iterator i = Args.begin();
  const VarDecl *ThisArg = i->first;
  llvm::Value *ThisObj = GetAddrOfLocalVar(ThisArg);
  llvm::Value *LoadOfThis = Builder.CreateLoad(ThisObj, "this");
  const VarDecl *SrcArg = (i+1)->first;
  llvm::Value *SrcObj = GetAddrOfLocalVar(SrcArg);
  llvm::Value *LoadOfSrc = Builder.CreateLoad(SrcObj);

  for (CXXRecordDecl::field_iterator I = ClassDecl->field_begin(),
       E = ClassDecl->field_end(); I != E; ++I) {
    const FieldDecl *Field = *I;
    
    QualType FieldType = getContext().getCanonicalType(Field->getType());
    const ConstantArrayType *Array =
      getContext().getAsConstantArrayType(FieldType);
    if (Array)
      FieldType = getContext().getBaseElementType(FieldType);

    if (const RecordType *FieldClassType = FieldType->getAs<RecordType>()) {
      CXXRecordDecl *FieldClassDecl
        = cast<CXXRecordDecl>(FieldClassType->getDecl());
      LValue LHS = EmitLValueForField(LoadOfThis, Field, 0);
      LValue RHS = EmitLValueForField(LoadOfSrc, Field, 0);
      if (Array) {
        const llvm::Type *BasePtr = ConvertType(FieldType);
        BasePtr = llvm::PointerType::getUnqual(BasePtr);
        llvm::Value *DestBaseAddrPtr =
          Builder.CreateBitCast(LHS.getAddress(), BasePtr);
        llvm::Value *SrcBaseAddrPtr =
          Builder.CreateBitCast(RHS.getAddress(), BasePtr);
        EmitClassAggrMemberwiseCopy(DestBaseAddrPtr, SrcBaseAddrPtr, Array,
                                    FieldClassDecl);
      }
      else
        EmitClassMemberwiseCopy(LHS.getAddress(), RHS.getAddress(),
                                FieldClassDecl);
      continue;
    }
    
    // Do a built-in assignment of scalar data members.
    LValue LHS = EmitLValueForFieldInitialization(LoadOfThis, Field, 0);
    LValue RHS = EmitLValueForFieldInitialization(LoadOfSrc, Field, 0);

    if (!hasAggregateLLVMType(Field->getType())) {
      RValue RVRHS = EmitLoadOfLValue(RHS, Field->getType());
      EmitStoreThroughLValue(RVRHS, LHS, Field->getType());
    } else if (Field->getType()->isAnyComplexType()) {
      ComplexPairTy Pair = LoadComplexFromAddr(RHS.getAddress(),
                                               RHS.isVolatileQualified());
      StoreComplexToAddr(Pair, LHS.getAddress(), LHS.isVolatileQualified());
    } else {
      EmitAggregateCopy(LHS.getAddress(), RHS.getAddress(), Field->getType());
    }
  }

  InitializeVTablePointers(ClassDecl);
}

/// SynthesizeCXXCopyAssignment - Implicitly define copy assignment operator.
/// Before the implicitly-declared copy assignment operator for a class is
/// implicitly defined, all implicitly- declared copy assignment operators for
/// its direct base classes and its nonstatic data members shall have been
/// implicitly defined. [12.8-p12]
/// The implicitly-defined copy assignment operator for class X performs
/// memberwise assignment of its subob- jects. The direct base classes of X are
/// assigned first, in the order of their declaration in
/// the base-specifier-list, and then the immediate nonstatic data members of X
/// are assigned, in the order in which they were declared in the class
/// definition.Each subobject is assigned in the manner appropriate to its type:
///   if the subobject is of class type, the copy assignment operator for the
///   class is used (as if by explicit qualification; that is, ignoring any
///   possible virtual overriding functions in more derived classes);
///
///   if the subobject is an array, each element is assigned, in the manner
///   appropriate to the element type;
///
///   if the subobject is of scalar type, the built-in assignment operator is
///   used.
void CodeGenFunction::SynthesizeCXXCopyAssignment(const FunctionArgList &Args) {
  const CXXMethodDecl *CD = cast<CXXMethodDecl>(CurGD.getDecl());
  const CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(CD->getDeclContext());
  assert(!ClassDecl->hasUserDeclaredCopyAssignment() &&
         "SynthesizeCXXCopyAssignment - copy assignment has user declaration");

  FunctionArgList::const_iterator i = Args.begin();
  const VarDecl *ThisArg = i->first;
  llvm::Value *ThisObj = GetAddrOfLocalVar(ThisArg);
  llvm::Value *LoadOfThis = Builder.CreateLoad(ThisObj, "this");
  const VarDecl *SrcArg = (i+1)->first;
  llvm::Value *SrcObj = GetAddrOfLocalVar(SrcArg);
  llvm::Value *LoadOfSrc = Builder.CreateLoad(SrcObj);

  for (CXXRecordDecl::base_class_const_iterator Base = ClassDecl->bases_begin();
       Base != ClassDecl->bases_end(); ++Base) {
    // FIXME. copy assignment of virtual base NYI
    if (Base->isVirtual())
      continue;

    CXXRecordDecl *BaseClassDecl
      = cast<CXXRecordDecl>(Base->getType()->getAs<RecordType>()->getDecl());
    EmitClassCopyAssignment(LoadOfThis, LoadOfSrc, ClassDecl, BaseClassDecl,
                            Base->getType());
  }

  for (CXXRecordDecl::field_iterator Field = ClassDecl->field_begin(),
       FieldEnd = ClassDecl->field_end();
       Field != FieldEnd; ++Field) {
    QualType FieldType = getContext().getCanonicalType((*Field)->getType());
    const ConstantArrayType *Array =
      getContext().getAsConstantArrayType(FieldType);
    if (Array)
      FieldType = getContext().getBaseElementType(FieldType);

    if (const RecordType *FieldClassType = FieldType->getAs<RecordType>()) {
      CXXRecordDecl *FieldClassDecl
      = cast<CXXRecordDecl>(FieldClassType->getDecl());
      LValue LHS = EmitLValueForField(LoadOfThis, *Field, 0);
      LValue RHS = EmitLValueForField(LoadOfSrc, *Field, 0);
      if (Array) {
        const llvm::Type *BasePtr = ConvertType(FieldType);
        BasePtr = llvm::PointerType::getUnqual(BasePtr);
        llvm::Value *DestBaseAddrPtr =
          Builder.CreateBitCast(LHS.getAddress(), BasePtr);
        llvm::Value *SrcBaseAddrPtr =
          Builder.CreateBitCast(RHS.getAddress(), BasePtr);
        EmitClassAggrCopyAssignment(DestBaseAddrPtr, SrcBaseAddrPtr, Array,
                                    FieldClassDecl, FieldType);
      }
      else
        EmitClassCopyAssignment(LHS.getAddress(), RHS.getAddress(),
                               0 /*ClassDecl*/, FieldClassDecl, FieldType);
      continue;
    }
    // Do a built-in assignment of scalar data members.
    LValue LHS = EmitLValueForField(LoadOfThis, *Field, 0);
    LValue RHS = EmitLValueForField(LoadOfSrc, *Field, 0);
    if (!hasAggregateLLVMType(Field->getType())) {
      RValue RVRHS = EmitLoadOfLValue(RHS, Field->getType());
      EmitStoreThroughLValue(RVRHS, LHS, Field->getType());
    } else if (Field->getType()->isAnyComplexType()) {
      ComplexPairTy Pair = LoadComplexFromAddr(RHS.getAddress(),
                                               RHS.isVolatileQualified());
      StoreComplexToAddr(Pair, LHS.getAddress(), LHS.isVolatileQualified());
    } else {
      EmitAggregateCopy(LHS.getAddress(), RHS.getAddress(), Field->getType());
    }
  }

  // return *this;
  Builder.CreateStore(LoadOfThis, ReturnValue);
}

static void EmitBaseInitializer(CodeGenFunction &CGF, 
                                const CXXRecordDecl *ClassDecl,
                                CXXBaseOrMemberInitializer *BaseInit,
                                CXXCtorType CtorType) {
  assert(BaseInit->isBaseInitializer() &&
         "Must have base initializer!");

  llvm::Value *ThisPtr = CGF.LoadCXXThis();
  
  const Type *BaseType = BaseInit->getBaseClass();
  CXXRecordDecl *BaseClassDecl =
    cast<CXXRecordDecl>(BaseType->getAs<RecordType>()->getDecl());

  bool isBaseVirtual = BaseInit->isBaseVirtual();

  // The base constructor doesn't construct virtual bases.
  if (CtorType == Ctor_Base && isBaseVirtual)
    return;

  // We can pretend to be a complete class because it only matters for
  // virtual bases, and we only do virtual bases for complete ctors.
  llvm::Value *V = ThisPtr;
  V = CGF.GetAddressOfBaseOfCompleteClass(V, isBaseVirtual,
                                          ClassDecl, BaseClassDecl);

  CGF.EmitAggExpr(BaseInit->getInit(), V, false, false, true);
  
  if (CGF.Exceptions && !BaseClassDecl->hasTrivialDestructor()) {
    // FIXME: Is this OK for C++0x delegating constructors?
    CodeGenFunction::EHCleanupBlock Cleanup(CGF);

    CXXDestructorDecl *DD = BaseClassDecl->getDestructor(CGF.getContext());
    CGF.EmitCXXDestructorCall(DD, Dtor_Base, V);
  }
}

static void EmitMemberInitializer(CodeGenFunction &CGF,
                                  const CXXRecordDecl *ClassDecl,
                                  CXXBaseOrMemberInitializer *MemberInit) {
  assert(MemberInit->isMemberInitializer() &&
         "Must have member initializer!");
  
  // non-static data member initializers.
  FieldDecl *Field = MemberInit->getMember();
  QualType FieldType = CGF.getContext().getCanonicalType(Field->getType());

  llvm::Value *ThisPtr = CGF.LoadCXXThis();
  LValue LHS = CGF.EmitLValueForFieldInitialization(ThisPtr, Field, 0);
  
  // If we are initializing an anonymous union field, drill down to the field.
  if (MemberInit->getAnonUnionMember()) {
    Field = MemberInit->getAnonUnionMember();
    LHS = CGF.EmitLValueForField(LHS.getAddress(), Field, 0);
    FieldType = Field->getType();
  }

  // FIXME: If there's no initializer and the CXXBaseOrMemberInitializer
  // was implicitly generated, we shouldn't be zeroing memory.
  RValue RHS;
  if (FieldType->isReferenceType()) {
    RHS = CGF.EmitReferenceBindingToExpr(MemberInit->getInit(),
                                         /*IsInitializer=*/true);
    CGF.EmitStoreThroughLValue(RHS, LHS, FieldType);
  } else if (FieldType->isArrayType() && !MemberInit->getInit()) {
    CGF.EmitMemSetToZero(LHS.getAddress(), Field->getType());
  } else if (!CGF.hasAggregateLLVMType(Field->getType())) {
    RHS = RValue::get(CGF.EmitScalarExpr(MemberInit->getInit(), true));
    CGF.EmitStoreThroughLValue(RHS, LHS, FieldType);
  } else if (MemberInit->getInit()->getType()->isAnyComplexType()) {
    CGF.EmitComplexExprIntoAddr(MemberInit->getInit(), LHS.getAddress(),
                                LHS.isVolatileQualified());
  } else {
    CGF.EmitAggExpr(MemberInit->getInit(), LHS.getAddress(), 
                    LHS.isVolatileQualified(), false, true);
    
    if (!CGF.Exceptions)
      return;

    const RecordType *RT = FieldType->getAs<RecordType>();
    if (!RT)
      return;
    
    CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
    if (!RD->hasTrivialDestructor()) {
      // FIXME: Is this OK for C++0x delegating constructors?
      CodeGenFunction::EHCleanupBlock Cleanup(CGF);
      
      llvm::Value *ThisPtr = CGF.LoadCXXThis();
      LValue LHS = CGF.EmitLValueForField(ThisPtr, Field, 0);

      CXXDestructorDecl *DD = RD->getDestructor(CGF.getContext());
      CGF.EmitCXXDestructorCall(DD, Dtor_Complete, LHS.getAddress());
    }
  }
}

/// Checks whether the given constructor is a valid subject for the
/// complete-to-base constructor delegation optimization, i.e.
/// emitting the complete constructor as a simple call to the base
/// constructor.
static bool IsConstructorDelegationValid(const CXXConstructorDecl *Ctor) {

  // Currently we disable the optimization for classes with virtual
  // bases because (1) the addresses of parameter variables need to be
  // consistent across all initializers but (2) the delegate function
  // call necessarily creates a second copy of the parameter variable.
  //
  // The limiting example (purely theoretical AFAIK):
  //   struct A { A(int &c) { c++; } };
  //   struct B : virtual A {
  //     B(int count) : A(count) { printf("%d\n", count); }
  //   };
  // ...although even this example could in principle be emitted as a
  // delegation since the address of the parameter doesn't escape.
  if (Ctor->getParent()->getNumVBases()) {
    // TODO: white-list trivial vbase initializers.  This case wouldn't
    // be subject to the restrictions below.

    // TODO: white-list cases where:
    //  - there are no non-reference parameters to the constructor
    //  - the initializers don't access any non-reference parameters
    //  - the initializers don't take the address of non-reference
    //    parameters
    //  - etc.
    // If we ever add any of the above cases, remember that:
    //  - function-try-blocks will always blacklist this optimization
    //  - we need to perform the constructor prologue and cleanup in
    //    EmitConstructorBody.

    return false;
  }

  // We also disable the optimization for variadic functions because
  // it's impossible to "re-pass" varargs.
  if (Ctor->getType()->getAs<FunctionProtoType>()->isVariadic())
    return false;

  return true;
}

/// EmitConstructorBody - Emits the body of the current constructor.
void CodeGenFunction::EmitConstructorBody(FunctionArgList &Args) {
  const CXXConstructorDecl *Ctor = cast<CXXConstructorDecl>(CurGD.getDecl());
  CXXCtorType CtorType = CurGD.getCtorType();

  // Before we go any further, try the complete->base constructor
  // delegation optimization.
  if (CtorType == Ctor_Complete && IsConstructorDelegationValid(Ctor)) {
    EmitDelegateCXXConstructorCall(Ctor, Ctor_Base, Args);
    return;
  }

  Stmt *Body = Ctor->getBody();

  // Enter the function-try-block before the constructor prologue if
  // applicable.
  CXXTryStmtInfo TryInfo;
  bool IsTryBody = (Body && isa<CXXTryStmt>(Body));

  if (IsTryBody)
    TryInfo = EnterCXXTryStmt(*cast<CXXTryStmt>(Body));

  unsigned CleanupStackSize = CleanupEntries.size();

  // Emit the constructor prologue, i.e. the base and member
  // initializers.
  EmitCtorPrologue(Ctor, CtorType);

  // Emit the body of the statement.
  if (IsTryBody)
    EmitStmt(cast<CXXTryStmt>(Body)->getTryBlock());
  else if (Body)
    EmitStmt(Body);
  else {
    assert(Ctor->isImplicit() && "bodyless ctor not implicit");
    if (!Ctor->isDefaultConstructor()) {
      assert(Ctor->isCopyConstructor());
      SynthesizeCXXCopyConstructor(Args);
    }
  }

  // Emit any cleanup blocks associated with the member or base