CGCXX.cpp

//===--- CGDecl.cpp - Emit LLVM Code for declarations ---------------------===//
//
//                     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.
//
//===----------------------------------------------------------------------===//

// We might split this into multiple files if it gets too unwieldy

#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include "Mangle.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/StmtCXX.h"
#include "llvm/ADT/StringExtras.h"
using namespace clang;
using namespace CodeGen;

void
CodeGenFunction::EmitCXXGlobalDtorRegistration(llvm::Constant *DtorFn,
                                               llvm::Constant *DeclPtr) {
  const llvm::Type *Int8PtrTy = 
    llvm::Type::getInt8Ty(VMContext)->getPointerTo();

  std::vector<const llvm::Type *> Params;
  Params.push_back(Int8PtrTy);

  // Get the destructor function type
  const llvm::Type *DtorFnTy =
    llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext), Params, false);
  DtorFnTy = llvm::PointerType::getUnqual(DtorFnTy);

  Params.clear();
  Params.push_back(DtorFnTy);
  Params.push_back(Int8PtrTy);
  Params.push_back(Int8PtrTy);

  // Get the __cxa_atexit function type
  // extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
  const llvm::FunctionType *AtExitFnTy =
    llvm::FunctionType::get(ConvertType(getContext().IntTy), Params, false);

  llvm::Constant *AtExitFn = CGM.CreateRuntimeFunction(AtExitFnTy,
                                                       "__cxa_atexit");

  llvm::Constant *Handle = CGM.CreateRuntimeVariable(Int8PtrTy,
                                                     "__dso_handle");
  llvm::Value *Args[3] = { llvm::ConstantExpr::getBitCast(DtorFn, DtorFnTy),
                           llvm::ConstantExpr::getBitCast(DeclPtr, Int8PtrTy),
                           llvm::ConstantExpr::getBitCast(Handle, Int8PtrTy) };
  Builder.CreateCall(AtExitFn, &Args[0], llvm::array_endof(Args));
}

void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
                                               llvm::Constant *DeclPtr) {
  assert(D.hasGlobalStorage() &&
         "VarDecl must have global storage!");

  const Expr *Init = D.getInit();
  QualType T = D.getType();
  bool isVolatile = getContext().getCanonicalType(T).isVolatileQualified();

  if (T->isReferenceType()) {
    ErrorUnsupported(Init, "global variable that binds to a reference");
  } else if (!hasAggregateLLVMType(T)) {
    llvm::Value *V = EmitScalarExpr(Init);
    EmitStoreOfScalar(V, DeclPtr, isVolatile, T);
  } else if (T->isAnyComplexType()) {
    EmitComplexExprIntoAddr(Init, DeclPtr, isVolatile);
  } else {
    EmitAggExpr(Init, DeclPtr, isVolatile);
    // Avoid generating destructor(s) for initialized objects. 
    if (!isa<CXXConstructExpr>(Init))
      return;
    const ConstantArrayType *Array = getContext().getAsConstantArrayType(T);
    if (Array)
      T = getContext().getBaseElementType(Array);
    
    if (const RecordType *RT = T->getAs<RecordType>()) {
      CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
      if (!RD->hasTrivialDestructor()) {
        llvm::Constant *DtorFn;
        if (Array) {
          DtorFn = CodeGenFunction(CGM).GenerateCXXAggrDestructorHelper(
                                                RD->getDestructor(getContext()), 
                                                Array, DeclPtr);
          DeclPtr = 
            llvm::Constant::getNullValue(llvm::Type::getInt8PtrTy(VMContext));
        }
        else
          DtorFn = CGM.GetAddrOfCXXDestructor(RD->getDestructor(getContext()), 
                                              Dtor_Complete);                                
        EmitCXXGlobalDtorRegistration(DtorFn, DeclPtr);
      }
    }
  }
}

void
CodeGenModule::EmitCXXGlobalInitFunc() {
  if (CXXGlobalInits.empty())
    return;

  const llvm::FunctionType *FTy
    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
                              false);

  // Create our global initialization function.
  // FIXME: Should this be tweakable by targets?
  llvm::Function *Fn =
    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
                           "__cxx_global_initialization", &TheModule);

  CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
                                                   &CXXGlobalInits[0],
                                                   CXXGlobalInits.size());
  AddGlobalCtor(Fn);
}

void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
                                                const VarDecl **Decls,
                                                unsigned NumDecls) {
  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
                SourceLocation());

  for (unsigned i = 0; i != NumDecls; ++i) {
    const VarDecl *D = Decls[i];

    llvm::Constant *DeclPtr = CGM.GetAddrOfGlobalVar(D);
    EmitCXXGlobalVarDeclInit(*D, DeclPtr);
  }
  FinishFunction();
}

void
CodeGenFunction::EmitStaticCXXBlockVarDeclInit(const VarDecl &D,
                                               llvm::GlobalVariable *GV) {
  // FIXME: This should use __cxa_guard_{acquire,release}?

  assert(!getContext().getLangOptions().ThreadsafeStatics &&
         "thread safe statics are currently not supported!");

  llvm::SmallString<256> GuardVName;
  llvm::raw_svector_ostream GuardVOut(GuardVName);
  mangleGuardVariable(CGM.getMangleContext(), &D, GuardVOut);

  // Create the guard variable.
  llvm::GlobalValue *GuardV =
    new llvm::GlobalVariable(CGM.getModule(), llvm::Type::getInt64Ty(VMContext),
                             false, GV->getLinkage(),
                llvm::Constant::getNullValue(llvm::Type::getInt64Ty(VMContext)),
                             GuardVName.str());

  // Load the first byte of the guard variable.
  const llvm::Type *PtrTy
    = llvm::PointerType::get(llvm::Type::getInt8Ty(VMContext), 0);
  llvm::Value *V = Builder.CreateLoad(Builder.CreateBitCast(GuardV, PtrTy),
                                      "tmp");

  // Compare it against 0.
  llvm::Value *nullValue
    = llvm::Constant::getNullValue(llvm::Type::getInt8Ty(VMContext));
  llvm::Value *ICmp = Builder.CreateICmpEQ(V, nullValue , "tobool");

  llvm::BasicBlock *InitBlock = createBasicBlock("init");
  llvm::BasicBlock *EndBlock = createBasicBlock("init.end");

  // If the guard variable is 0, jump to the initializer code.
  Builder.CreateCondBr(ICmp, InitBlock, EndBlock);

  EmitBlock(InitBlock);

  EmitCXXGlobalVarDeclInit(D, GV);

  Builder.CreateStore(llvm::ConstantInt::get(llvm::Type::getInt8Ty(VMContext),
                                             1),
                      Builder.CreateBitCast(GuardV, PtrTy));

  EmitBlock(EndBlock);
}

RValue CodeGenFunction::EmitCXXMemberCall(const CXXMethodDecl *MD,
                                          llvm::Value *Callee,
                                          llvm::Value *This,
                                          CallExpr::const_arg_iterator ArgBeg,
                                          CallExpr::const_arg_iterator ArgEnd) {
  assert(MD->isInstance() &&
         "Trying to emit a member call expr on a static method!");

  // A call to a trivial destructor requires no code generation.
  if (const CXXDestructorDecl *Destructor = dyn_cast<CXXDestructorDecl>(MD))
    if (Destructor->isTrivial())
      return RValue::get(0);

  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();

  CallArgList Args;

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

  // And the rest of the call args
  EmitCallArgs(Args, FPT, ArgBeg, ArgEnd);

  QualType ResultType = MD->getType()->getAs<FunctionType>()->getResultType();
  return EmitCall(CGM.getTypes().getFunctionInfo(ResultType, Args),
                  Callee, Args, MD);
}

/// canDevirtualizeMemberFunctionCalls - Checks whether virtual calls on given
/// expr can be devirtualized.
static bool canDevirtualizeMemberFunctionCalls(const Expr *Base) {
  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Base)) {
    if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
      // This is a record decl. We know the type and can devirtualize it.
      return VD->getType()->isRecordType();
    }
    
    return false;
  }
  
  // We can always devirtualize calls on temporary object expressions.
  if (isa<CXXTemporaryObjectExpr>(Base))
    return true;
  
  // And calls on bound temporaries.
  if (isa<CXXBindTemporaryExpr>(Base))
    return true;
  
  // Check if this is a call expr that returns a record type.
  if (const CallExpr *CE = dyn_cast<CallExpr>(Base))
    return CE->getCallReturnType()->isRecordType();
  
  // We can't devirtualize the call.
  return false;
}

RValue CodeGenFunction::EmitCXXMemberCallExpr(const CXXMemberCallExpr *CE) {
  if (isa<BinaryOperator>(CE->getCallee())) 
    return EmitCXXMemberPointerCallExpr(CE);
      
  const MemberExpr *ME = cast<MemberExpr>(CE->getCallee());
  const CXXMethodDecl *MD = cast<CXXMethodDecl>(ME->getMemberDecl());

  if (MD->isStatic()) {
    // The method is static, emit it as we would a regular call.
    llvm::Value *Callee = CGM.GetAddrOfFunction(MD);
    return EmitCall(Callee, getContext().getPointerType(MD->getType()),
                    CE->arg_begin(), CE->arg_end(), 0);
    
  }
  
  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();

  const llvm::Type *Ty =
    CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(MD),
                                   FPT->isVariadic());
  llvm::Value *This;

  if (ME->isArrow())
    This = EmitScalarExpr(ME->getBase());
  else {
    LValue BaseLV = EmitLValue(ME->getBase());
    This = BaseLV.getAddress();
  }

  // C++ [class.virtual]p12:
  //   Explicit qualification with the scope operator (5.1) suppresses the
  //   virtual call mechanism.
  //
  // We also don't emit a virtual call if the base expression has a record type
  // because then we know what the type is.
  llvm::Value *Callee;
  if (MD->isVirtual() && !ME->hasQualifier() && 
      !canDevirtualizeMemberFunctionCalls(ME->getBase()))
    Callee = BuildVirtualCall(MD, This, Ty);
  else if (const CXXDestructorDecl *Destructor
             = dyn_cast<CXXDestructorDecl>(MD))
    Callee = CGM.GetAddrOfFunction(GlobalDecl(Destructor, Dtor_Complete), Ty);
  else
    Callee = CGM.GetAddrOfFunction(MD, Ty);

  return EmitCXXMemberCall(MD, Callee, This,
                           CE->arg_begin(), CE->arg_end());
}

RValue
CodeGenFunction::EmitCXXMemberPointerCallExpr(const CXXMemberCallExpr *E) {
  const BinaryOperator *BO = cast<BinaryOperator>(E->getCallee());
  const Expr *BaseExpr = BO->getLHS();
  const Expr *MemFnExpr = BO->getRHS();
  
  const MemberPointerType *MPT = 
    MemFnExpr->getType()->getAs<MemberPointerType>();
  const FunctionProtoType *FPT = 
    MPT->getPointeeType()->getAs<FunctionProtoType>();
  const CXXRecordDecl *RD = 
    cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl());

  const llvm::FunctionType *FTy = 
    CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(RD, FPT),
                                   FPT->isVariadic());

  const llvm::Type *Int8PtrTy = 
    llvm::Type::getInt8Ty(VMContext)->getPointerTo();

  // Get the member function pointer.
  llvm::Value *MemFnPtr = 
    CreateTempAlloca(ConvertType(MemFnExpr->getType()), "mem.fn");
  EmitAggExpr(MemFnExpr, MemFnPtr, /*VolatileDest=*/false);

  // Emit the 'this' pointer.
  llvm::Value *This;
  
  if (BO->getOpcode() == BinaryOperator::PtrMemI)
    This = EmitScalarExpr(BaseExpr);
  else 
    This = EmitLValue(BaseExpr).getAddress();
  
  // Adjust it.
  llvm::Value *Adj = Builder.CreateStructGEP(MemFnPtr, 1);
  Adj = Builder.CreateLoad(Adj, "mem.fn.adj");
  
  llvm::Value *Ptr = Builder.CreateBitCast(This, Int8PtrTy, "ptr");
  Ptr = Builder.CreateGEP(Ptr, Adj, "adj");
  
  This = Builder.CreateBitCast(Ptr, This->getType(), "this");
  
  llvm::Value *FnPtr = Builder.CreateStructGEP(MemFnPtr, 0, "mem.fn.ptr");
  
  const llvm::Type *PtrDiffTy = ConvertType(getContext().getPointerDiffType());

  llvm::Value *FnAsInt = Builder.CreateLoad(FnPtr, "fn");
  
  // If the LSB in the function pointer is 1, the function pointer points to
  // a virtual function.
  llvm::Value *IsVirtual 
    = Builder.CreateAnd(FnAsInt, llvm::ConstantInt::get(PtrDiffTy, 1),
                        "and");
  
  IsVirtual = Builder.CreateTrunc(IsVirtual,
                                  llvm::Type::getInt1Ty(VMContext));
  
  llvm::BasicBlock *FnVirtual = createBasicBlock("fn.virtual");
  llvm::BasicBlock *FnNonVirtual = createBasicBlock("fn.nonvirtual");
  llvm::BasicBlock *FnEnd = createBasicBlock("fn.end");
  
  Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual);
  EmitBlock(FnVirtual);
  
  const llvm::Type *VTableTy = 
    FTy->getPointerTo()->getPointerTo()->getPointerTo();

  llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy);
  VTable = Builder.CreateLoad(VTable);
  
  VTable = Builder.CreateGEP(VTable, FnAsInt, "fn");
  
  // Since the function pointer is 1 plus the virtual table offset, we
  // subtract 1 by using a GEP.
  VTable = Builder.CreateConstGEP1_64(VTable, (uint64_t)-1);
  
  llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "virtualfn");
  
  EmitBranch(FnEnd);
  EmitBlock(FnNonVirtual);
  
  // If the function is not virtual, just load the pointer.
  llvm::Value *NonVirtualFn = Builder.CreateLoad(FnPtr, "fn");
  NonVirtualFn = Builder.CreateIntToPtr(NonVirtualFn, FTy->getPointerTo());
  
  EmitBlock(FnEnd);

  llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo());
  Callee->reserveOperandSpace(2);
  Callee->addIncoming(VirtualFn, FnVirtual);
  Callee->addIncoming(NonVirtualFn, FnNonVirtual);

  CallArgList Args;

  QualType ThisType = 
    getContext().getPointerType(getContext().getTagDeclType(RD));

  // Push the this ptr.
  Args.push_back(std::make_pair(RValue::get(This), ThisType));
  
  // And the rest of the call args
  EmitCallArgs(Args, FPT, E->arg_begin(), E->arg_end());
  QualType ResultType = BO->getType()->getAs<FunctionType>()->getResultType();
  return EmitCall(CGM.getTypes().getFunctionInfo(ResultType, Args),
                  Callee, Args, 0);
}

RValue
CodeGenFunction::EmitCXXOperatorMemberCallExpr(const CXXOperatorCallExpr *E,
                                               const CXXMethodDecl *MD) {
  assert(MD->isInstance() &&
         "Trying to emit a member call expr on a static method!");

  if (MD->isCopyAssignment()) {
    const CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(MD->getDeclContext());
    if (ClassDecl->hasTrivialCopyAssignment()) {
      assert(!ClassDecl->hasUserDeclaredCopyAssignment() &&
             "EmitCXXOperatorMemberCallExpr - user declared copy assignment");
      llvm::Value *This = EmitLValue(E->getArg(0)).getAddress();
      llvm::Value *Src = EmitLValue(E->getArg(1)).getAddress();
      QualType Ty = E->getType();
      EmitAggregateCopy(This, Src, Ty);
      return RValue::get(This);
    }
  }

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

  llvm::Value *This = EmitLValue(E->getArg(0)).getAddress();

  return EmitCXXMemberCall(MD, Callee, This,
                           E->arg_begin() + 1, E->arg_end());
}

llvm::Value *CodeGenFunction::LoadCXXThis() {
  assert(isa<CXXMethodDecl>(CurFuncDecl) &&
         "Must be in a C++ member function decl to load 'this'");
  assert(cast<CXXMethodDecl>(CurFuncDecl)->isInstance() &&
         "Must be in a C++ member function decl to load 'this'");

  // FIXME: What if we're inside a block?
  // ans: See how CodeGenFunction::LoadObjCSelf() uses
  // CodeGenFunction::BlockForwardSelf() for how to do this.
  return Builder.CreateLoad(LocalDeclMap[CXXThisDecl], "this");
}

/// EmitCXXAggrConstructorCall - This routine essentially creates a (nested)
/// for-loop to call the default constructor on individual members of the
/// array. 
/// 'D' is the default constructor for elements of the array, 'ArrayTy' is the
/// array type and 'ArrayPtr' points to the beginning fo the array.
/// It is assumed that all relevant checks have been made by the caller.
void
CodeGenFunction::EmitCXXAggrConstructorCall(const CXXConstructorDecl *D,
                                            const ConstantArrayType *ArrayTy,
                                            llvm::Value *ArrayPtr) {
  const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
  llvm::Value * NumElements =
    llvm::ConstantInt::get(SizeTy, 
                           getContext().getConstantArrayElementCount(ArrayTy));

  EmitCXXAggrConstructorCall(D, NumElements, ArrayPtr);
}

void
CodeGenFunction::EmitCXXAggrConstructorCall(const CXXConstructorDecl *D,
                                            llvm::Value *NumElements,
                                            llvm::Value *ArrayPtr) {
  const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());

  // Create a temporary for the loop index and initialize it with 0.
  llvm::Value *IndexPtr = CreateTempAlloca(SizeTy, "loop.index");
  llvm::Value *Zero = llvm::Constant::getNullValue(SizeTy);
  Builder.CreateStore(Zero, IndexPtr, false);

  // 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.
  llvm::Value *Counter = Builder.CreateLoad(IndexPtr);
  llvm::Value *IsLess = Builder.CreateICmpULT(Counter, NumElements, "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);
  llvm::Value *Address = Builder.CreateInBoundsGEP(ArrayPtr, Counter, 
                                                   "arrayidx");
  EmitCXXConstructorCall(D, Ctor_Complete, Address, 0, 0);

  EmitBlock(ContinueBlock);

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

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

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

/// EmitCXXAggrDestructorCall - calls the default destructor on array
/// elements in reverse order of construction.
void
CodeGenFunction::EmitCXXAggrDestructorCall(const CXXDestructorDecl *D,
                                           const ArrayType *Array,
                                           llvm::Value *This) {
  const ConstantArrayType *CA = dyn_cast<ConstantArrayType>(Array);
  assert(CA && "Do we support VLA for destruction ?");
  llvm::Value *One = llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext),
                                            1);
  uint64_t ElementCount = getContext().getConstantArrayElementCount(CA);
  // Create a temporary for the loop index and initialize it with count of
  // array elements.
  llvm::Value *IndexPtr = CreateTempAlloca(llvm::Type::getInt64Ty(VMContext),
                                           "loop.index");
  // Index = ElementCount;
  llvm::Value* UpperCount =
    llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), ElementCount);
  Builder.CreateStore(UpperCount, IndexPtr, false);

  // 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 != 0 fall to the loop body,
  // otherwise, go to the block after the for-loop.
  llvm::Value* zeroConstant =
    llvm::Constant::getNullValue(llvm::Type::getInt64Ty(VMContext));
  llvm::Value *Counter = Builder.CreateLoad(IndexPtr);
  llvm::Value *IsNE = Builder.CreateICmpNE(Counter, zeroConstant,
                                            "isne");
  // If the condition is true, execute the body.
  Builder.CreateCondBr(IsNE, 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);
  Counter = Builder.CreateSub(Counter, One);
  llvm::Value *Address = Builder.CreateInBoundsGEP(This, Counter, "arrayidx");
  EmitCXXDestructorCall(D, Dtor_Complete, Address);

  EmitBlock(ContinueBlock);

  // Emit the decrement of the loop counter.
  Counter = Builder.CreateLoad(IndexPtr);
  Counter = Builder.CreateSub(Counter, One, "dec");
  Builder.CreateStore(Counter, IndexPtr, false);

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

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

/// EmitCXXAggrDestructorCall - Generates a helper function which when invoked,
/// calls the default destructor on array elements in reverse order of 
/// construction.
llvm::Constant * 
CodeGenFunction::GenerateCXXAggrDestructorHelper(const CXXDestructorDecl *D,
                                                 const ArrayType *Array,
                                                 llvm::Value *This) {
  static int UniqueCount;
  FunctionArgList Args;
  ImplicitParamDecl *Dst =
    ImplicitParamDecl::Create(getContext(), 0,
                              SourceLocation(), 0,
                              getContext().getPointerType(getContext().VoidTy));
  Args.push_back(std::make_pair(Dst, Dst->getType()));
  
  llvm::SmallString<16> Name;
  llvm::raw_svector_ostream(Name) << "__tcf_" << (++UniqueCount);
  QualType R = getContext().VoidTy;
  const CGFunctionInfo &FI = CGM.getTypes().getFunctionInfo(R, Args);
  const llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI, false);
  llvm::Function *Fn =
    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
                           Name.c_str(),
                           &CGM.getModule());
  IdentifierInfo *II
    = &CGM.getContext().Idents.get(Name.c_str());
  FunctionDecl *FD = FunctionDecl::Create(getContext(),
                                          getContext().getTranslationUnitDecl(),
                                          SourceLocation(), II, R, 0,
                                          FunctionDecl::Static,
                                          false, true);
  StartFunction(FD, R, Fn, Args, SourceLocation());
  QualType BaseElementTy = getContext().getBaseElementType(Array);
  const llvm::Type *BasePtr = ConvertType(BaseElementTy);
  BasePtr = llvm::PointerType::getUnqual(BasePtr);
  llvm::Value *BaseAddrPtr = Builder.CreateBitCast(This, BasePtr);
  EmitCXXAggrDestructorCall(D, Array, BaseAddrPtr);
  FinishFunction();
  llvm::Type *Ptr8Ty = llvm::PointerType::get(llvm::Type::getInt8Ty(VMContext),
                                              0);
  llvm::Constant *m = llvm::ConstantExpr::getBitCast(Fn, Ptr8Ty);
  return m;
}

void
CodeGenFunction::EmitCXXConstructorCall(const CXXConstructorDecl *D,
                                        CXXCtorType Type,
                                        llvm::Value *This,
                                        CallExpr::const_arg_iterator ArgBeg,
                                        CallExpr::const_arg_iterator ArgEnd) {
  if (D->isCopyConstructor(getContext())) {
    const CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(D->getDeclContext());
    if (ClassDecl->hasTrivialCopyConstructor()) {
      assert(!ClassDecl->hasUserDeclaredCopyConstructor() &&
             "EmitCXXConstructorCall - user declared copy constructor");
      const Expr *E = (*ArgBeg);
      QualType Ty = E->getType();
      llvm::Value *Src = EmitLValue(E).getAddress();
      EmitAggregateCopy(This, Src, Ty);
      return;
    }
  }

  llvm::Value *Callee = CGM.GetAddrOfCXXConstructor(D, Type);

  EmitCXXMemberCall(D, Callee, This, ArgBeg, ArgEnd);
}

void CodeGenFunction::EmitCXXDestructorCall(const CXXDestructorDecl *D,
                                            CXXDtorType Type,
                                            llvm::Value *This) {
  llvm::Value *Callee = CGM.GetAddrOfCXXDestructor(D, Type);

  EmitCXXMemberCall(D, Callee, This, 0, 0);
}

void
CodeGenFunction::EmitCXXConstructExpr(llvm::Value *Dest,
                                      const CXXConstructExpr *E) {
  assert(Dest && "Must have a destination!");
  const CXXConstructorDecl *CD = E->getConstructor();
  const ConstantArrayType *Array =
    getContext().getAsConstantArrayType(E->getType());
  // For a copy constructor, even if it is trivial, must fall thru so
  // its argument is code-gen'ed.
  if (!CD->isCopyConstructor(getContext())) {
    QualType InitType = E->getType();
    if (Array)
      InitType = getContext().getBaseElementType(Array);
    const CXXRecordDecl *RD =
      cast<CXXRecordDecl>(InitType->getAs<RecordType>()->getDecl());
    if (RD->hasTrivialConstructor())
    return;
  }
  // Code gen optimization to eliminate copy constructor and return
  // its first argument instead.
  if (getContext().getLangOptions().ElideConstructors && E->isElidable()) {
    const Expr *Arg = E->getArg(0);
    
    if (const CXXBindTemporaryExpr *BindExpr = 
          dyn_cast<CXXBindTemporaryExpr>(Arg))
      Arg = BindExpr->getSubExpr();

    EmitAggExpr(Arg, Dest, false);
    return;
  }
  if (Array) {
    QualType BaseElementTy = getContext().getBaseElementType(Array);
    const llvm::Type *BasePtr = ConvertType(BaseElementTy);
    BasePtr = llvm::PointerType::getUnqual(BasePtr);
    llvm::Value *BaseAddrPtr =
      Builder.CreateBitCast(Dest, BasePtr);
    EmitCXXAggrConstructorCall(CD, Array, BaseAddrPtr);
  }
  else
    // Call the constructor.
    EmitCXXConstructorCall(CD, Ctor_Complete, Dest,
                           E->arg_begin(), E->arg_end());
}

void CodeGenModule::EmitCXXConstructors(const CXXConstructorDecl *D) {
  EmitGlobal(GlobalDecl(D, Ctor_Complete));
  EmitGlobal(GlobalDecl(D, Ctor_Base));
}

void CodeGenModule::EmitCXXConstructor(const CXXConstructorDecl *D,
                                       CXXCtorType Type) {

  llvm::Function *Fn = GetAddrOfCXXConstructor(D, Type);

  CodeGenFunction(*this).GenerateCode(GlobalDecl(D, Type), Fn);

  SetFunctionDefinitionAttributes(D, Fn);
  SetLLVMFunctionAttributesForDefinition(D, Fn);
}

llvm::Function *
CodeGenModule::GetAddrOfCXXConstructor(const CXXConstructorDecl *D,
                                       CXXCtorType Type) {
  const FunctionProtoType *FPT = D->getType()->getAs<FunctionProtoType>();
  const llvm::FunctionType *FTy =
    getTypes().GetFunctionType(getTypes().getFunctionInfo(D), 
                               FPT->isVariadic());

  const char *Name = getMangledCXXCtorName(D, Type);
  return cast<llvm::Function>(
                      GetOrCreateLLVMFunction(Name, FTy, GlobalDecl(D, Type)));
}

const char *CodeGenModule::getMangledCXXCtorName(const CXXConstructorDecl *D,
                                                 CXXCtorType Type) {
  llvm::SmallString<256> Name;
  llvm::raw_svector_ostream Out(Name);
  mangleCXXCtor(getMangleContext(), D, Type, Out);

  Name += '\0';
  return UniqueMangledName(Name.begin(), Name.end());
}

void CodeGenModule::EmitCXXDestructors(const CXXDestructorDecl *D) {
  EmitCXXDestructor(D, Dtor_Complete);
  EmitCXXDestructor(D, Dtor_Base);
}

void CodeGenModule::EmitCXXDestructor(const CXXDestructorDecl *D,
                                      CXXDtorType Type) {
  llvm::Function *Fn = GetAddrOfCXXDestructor(D, Type);

  CodeGenFunction(*this).GenerateCode(GlobalDecl(D, Type), Fn);

  SetFunctionDefinitionAttributes(D, Fn);
  SetLLVMFunctionAttributesForDefinition(D, Fn);
}

llvm::Function *
CodeGenModule::GetAddrOfCXXDestructor(const CXXDestructorDecl *D,
                                      CXXDtorType Type) {
  const llvm::FunctionType *FTy =
    getTypes().GetFunctionType(getTypes().getFunctionInfo(D), false);

  const char *Name = getMangledCXXDtorName(D, Type);
  return cast<llvm::Function>(
                      GetOrCreateLLVMFunction(Name, FTy, GlobalDecl(D, Type)));
}

const char *CodeGenModule::getMangledCXXDtorName(const CXXDestructorDecl *D,
                                                 CXXDtorType Type) {
  llvm::SmallString<256> Name;
  llvm::raw_svector_ostream Out(Name);
  mangleCXXDtor(getMangleContext(), D, Type, Out);

  Name += '\0';
  return UniqueMangledName(Name.begin(), Name.end());
}

llvm::Constant *CodeGenFunction::GenerateThunk(llvm::Function *Fn,
                                               const CXXMethodDecl *MD,
                                               bool Extern, int64_t nv,
                                               int64_t v) {
  return GenerateCovariantThunk(Fn, MD, Extern, nv, v, 0, 0);
}

llvm::Value *CodeGenFunction::DynamicTypeAdjust(llvm::Value *V, int64_t nv,
                                                int64_t v) {
  llvm::Type *Ptr8Ty = llvm::PointerType::get(llvm::Type::getInt8Ty(VMContext),
                                              0);
  const llvm::Type *OrigTy = V->getType();
  if (nv) {
    // Do the non-virtual adjustment
    V = Builder.CreateBitCast(V, Ptr8Ty);
    V = Builder.CreateConstInBoundsGEP1_64(V, nv);
    V = Builder.CreateBitCast(V, OrigTy);
  }
  if (v) {
    // Do the virtual this adjustment
    const llvm::Type *PtrDiffTy = 
      ConvertType(getContext().getPointerDiffType());
    llvm::Type *PtrPtr8Ty, *PtrPtrDiffTy;
    PtrPtr8Ty = llvm::PointerType::get(Ptr8Ty, 0);
    PtrPtrDiffTy = llvm::PointerType::get(PtrDiffTy, 0);
    llvm::Value *ThisVal = Builder.CreateBitCast(V, Ptr8Ty);
    V = Builder.CreateBitCast(V, PtrPtrDiffTy->getPointerTo());
    V = Builder.CreateLoad(V, "vtable");
    llvm::Value *VTablePtr = V;
    assert(v % (LLVMPointerWidth/8) == 0 && "vtable entry unaligned");
    v /= LLVMPointerWidth/8;
    V = Builder.CreateConstInBoundsGEP1_64(VTablePtr, v);
    V = Builder.CreateLoad(V);
    V = Builder.CreateGEP(ThisVal, V);
    V = Builder.CreateBitCast(V, OrigTy);
  }
  return V;
}

llvm::Constant *CodeGenFunction::GenerateCovariantThunk(llvm::Function *Fn,
                                                        const CXXMethodDecl *MD,
                                                        bool Extern,
                                                        int64_t nv_t,
                                                        int64_t v_t,
                                                        int64_t nv_r,
                                                        int64_t v_r) {
  QualType ResultType = MD->getType()->getAs<FunctionType>()->getResultType();

  FunctionArgList Args;
  ImplicitParamDecl *ThisDecl =
    ImplicitParamDecl::Create(getContext(), 0, SourceLocation(), 0,
                              MD->getThisType(getContext()));
  Args.push_back(std::make_pair(ThisDecl, ThisDecl->getType()));
  for (FunctionDecl::param_const_iterator i = MD->param_begin(),
         e = MD->param_end();
       i != e; ++i) {
    ParmVarDecl *D = *i;
    Args.push_back(std::make_pair(D, D->getType()));
  }
  IdentifierInfo *II
    = &CGM.getContext().Idents.get("__thunk_named_foo_");
  FunctionDecl *FD = FunctionDecl::Create(getContext(),
                                          getContext().getTranslationUnitDecl(),
                                          SourceLocation(), II, ResultType, 0,
                                          Extern
                                            ? FunctionDecl::Extern
                                            : FunctionDecl::Static,
                                          false, true);
  StartFunction(FD, ResultType, Fn, Args, SourceLocation());

  // generate body
  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
  const llvm::Type *Ty =
    CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(MD),
                                   FPT->isVariadic());
  llvm::Value *Callee = CGM.GetAddrOfFunction(MD, Ty);
  CallArgList CallArgs;

  QualType ArgType = MD->getThisType(getContext());
  llvm::Value *Arg = Builder.CreateLoad(LocalDeclMap[ThisDecl], "this");
  if (nv_t || v_t) {
    // Do the this adjustment.
    const llvm::Type *OrigTy = Callee->getType();
    Arg = DynamicTypeAdjust(Arg, nv_t, v_t);
    if (nv_r || v_r) {
      Callee = CGM.BuildCovariantThunk(MD, Extern, 0, 0, nv_r, v_r);
      Callee = Builder.CreateBitCast(Callee, OrigTy);
      nv_r = v_r = 0;
    }
  }    

  CallArgs.push_back(std::make_pair(RValue::get(Arg), ArgType));

  for (FunctionDecl::param_const_iterator i = MD->param_begin(),
         e = MD->param_end();
       i != e; ++i) {
    ParmVarDecl *D = *i;
    QualType ArgType = D->getType();

    // llvm::Value *Arg = CGF.GetAddrOfLocalVar(Dst);
    Expr *Arg = new (getContext()) DeclRefExpr(D, ArgType, SourceLocation());
    CallArgs.push_back(std::make_pair(EmitCallArg(Arg, ArgType), ArgType));
  }

  RValue RV = EmitCall(CGM.getTypes().getFunctionInfo(ResultType, CallArgs),
                       Callee, CallArgs, MD);
  if (nv_r || v_r) {
    bool CanBeZero = !(ResultType->isReferenceType()
    // FIXME: attr nonnull can't be zero either
                       /* || ResultType->hasAttr<NonNullAttr>() */ );
    // Do the return result adjustment.
    if (CanBeZero) {
      llvm::BasicBlock *NonZeroBlock = createBasicBlock();
      llvm::BasicBlock *ZeroBlock = createBasicBlock();
      llvm::BasicBlock *ContBlock = createBasicBlock();

      const llvm::Type *Ty = RV.getScalarVal()->getType();
      llvm::Value *Zero = llvm::Constant::getNullValue(Ty);
      Builder.CreateCondBr(Builder.CreateICmpNE(RV.getScalarVal(), Zero),
                           NonZeroBlock, ZeroBlock);
      EmitBlock(NonZeroBlock);
      llvm::Value *NZ = DynamicTypeAdjust(RV.getScalarVal(), nv_r, v_r);
      EmitBranch(ContBlock);
      EmitBlock(ZeroBlock);
      llvm::Value *Z = RV.getScalarVal();
      EmitBlock(ContBlock);
      llvm::PHINode *RVOrZero = Builder.CreatePHI(Ty);
      RVOrZero->reserveOperandSpace(2);
      RVOrZero->addIncoming(NZ, NonZeroBlock);
      RVOrZero->addIncoming(Z, ZeroBlock);
      RV = RValue::get(RVOrZero);
    } else
      RV = RValue::get(DynamicTypeAdjust(RV.getScalarVal(), nv_r, v_r));
  }

  if (!ResultType->isVoidType())
    EmitReturnOfRValue(RV, ResultType);

  FinishFunction();
  return Fn;
}

llvm::Constant *CodeGenModule::BuildThunk(const CXXMethodDecl *MD, bool Extern,
                                          int64_t nv, int64_t v) {
  llvm::SmallString<256> OutName;
  llvm::raw_svector_ostream Out(OutName);
  mangleThunk(getMangleContext(), MD, nv, v, Out);
  llvm::GlobalVariable::LinkageTypes linktype;
  linktype = llvm::GlobalValue::WeakAnyLinkage;
  if (!Extern)
    linktype = llvm::GlobalValue::InternalLinkage;
  llvm::Type *Ptr8Ty=llvm::PointerType::get(llvm::Type::getInt8Ty(VMContext),0);
  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
  const llvm::FunctionType *FTy =
    getTypes().GetFunctionType(getTypes().getFunctionInfo(MD),
                               FPT->isVariadic());

  llvm::Function *Fn = llvm::Function::Create(FTy, linktype, Out.str(),
                                              &getModule());
  CodeGenFunction(*this).GenerateThunk(Fn, MD, Extern, nv, v);
  llvm::Constant *m = llvm::ConstantExpr::getBitCast(Fn, Ptr8Ty);
  return m;
}

llvm::Constant *CodeGenModule::BuildCovariantThunk(const CXXMethodDecl *MD,
                                                   bool Extern, int64_t nv_t,
                                                   int64_t v_t, int64_t nv_r,
                                                   int64_t v_r) {
  llvm::SmallString<256> OutName;
  llvm::raw_svector_ostream Out(OutName);
  mangleCovariantThunk(getMangleContext(), MD, nv_t, v_t, nv_r, v_r, Out);
  llvm::GlobalVariable::LinkageTypes linktype;
  linktype = llvm::GlobalValue::WeakAnyLinkage;
  if (!Extern)
    linktype = llvm::GlobalValue::InternalLinkage;
  llvm::Type *Ptr8Ty=llvm::PointerType::get(llvm::Type::getInt8Ty(VMContext),0);
  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
  const llvm::FunctionType *FTy =
    getTypes().GetFunctionType(getTypes().getFunctionInfo(MD),
                               FPT->isVariadic());

  llvm::Function *Fn = llvm::Function::Create(FTy, linktype, Out.str(),
                                              &getModule());
  CodeGenFunction(*this).GenerateCovariantThunk(Fn, MD, Extern, nv_t, v_t, nv_r,
                                               v_r);
  llvm::Constant *m = llvm::ConstantExpr::getBitCast(Fn, Ptr8Ty);
  return m;
}

llvm::Value *
CodeGenFunction::GetVirtualCXXBaseClassOffset(llvm::Value *This,
                                              const CXXRecordDecl *ClassDecl,
                                           const CXXRecordDecl *BaseClassDecl) {
  const llvm::Type *Int8PtrTy = 
    llvm::Type::getInt8Ty(VMContext)->getPointerTo();

  llvm::Value *VTablePtr = Builder.CreateBitCast(This, 
                                                 Int8PtrTy->getPointerTo());
  VTablePtr = Builder.CreateLoad(VTablePtr, "vtable");

  int64_t VBaseOffsetIndex = 
    CGM.getVtableInfo().getVirtualBaseOffsetIndex(ClassDecl, BaseClassDecl);
  
  llvm::Value *VBaseOffsetPtr = 
    Builder.CreateConstGEP1_64(VTablePtr, VBaseOffsetIndex, "vbase.offset.ptr");
  const llvm::Type *PtrDiffTy = 
    ConvertType(getContext().getPointerDiffType());
  
  VBaseOffsetPtr = Builder.CreateBitCast(VBaseOffsetPtr, 
                                         PtrDiffTy->getPointerTo());
                                         
  llvm::Value *VBaseOffset = Builder.CreateLoad(VBaseOffsetPtr, "vbase.offset");
  
  return VBaseOffset;
}

static llvm::Value *BuildVirtualCall(CodeGenFunction &CGF, int64_t VtableIndex, 
                                     llvm::Value *This, const llvm::Type *Ty) {
  Ty = Ty->getPointerTo()->getPointerTo()->getPointerTo();
  
  llvm::Value *Vtable = CGF.Builder.CreateBitCast(This, Ty);
  Vtable = CGF.Builder.CreateLoad(Vtable);
  
  llvm::Value *VFuncPtr = 
    CGF.Builder.CreateConstInBoundsGEP1_64(Vtable, VtableIndex, "vfn");
  return CGF.Builder.CreateLoad(VFuncPtr);
}

llvm::Value *