void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI,
                                         llvm::Value *ReturnValue) {
  llvm::Value *RV = 0;

  // Functions with no result always return void.
  if (ReturnValue) {
    QualType RetTy = FI.getReturnType();
    const ABIArgInfo &RetAI = FI.getReturnInfo();

    switch (RetAI.getKind()) {
    case ABIArgInfo::Indirect:
      if (RetTy->isAnyComplexType()) {
        ComplexPairTy RT = LoadComplexFromAddr(ReturnValue, false);
        StoreComplexToAddr(RT, CurFn->arg_begin(), false);
      } else if (CodeGenFunction::hasAggregateLLVMType(RetTy)) {
        EmitAggregateCopy(CurFn->arg_begin(), ReturnValue, RetTy);
      } else {
        EmitStoreOfScalar(Builder.CreateLoad(ReturnValue), CurFn->arg_begin(),
                          false, RetTy);
      }
      break;

    case ABIArgInfo::Extend:
    case ABIArgInfo::Direct:
      // The internal return value temp always will have
      // pointer-to-return-type type.
      RV = Builder.CreateLoad(ReturnValue);
      break;

    case ABIArgInfo::Ignore:
      break;

    case ABIArgInfo::Coerce:
      RV = CreateCoercedLoad(ReturnValue, RetAI.getCoerceToType(), *this);
      break;

    case ABIArgInfo::Expand:
      assert(0 && "Invalid ABI kind for return argument");
    }
  }

  if (RV) {
    Builder.CreateRet(RV);
  } else {
    Builder.CreateRetVoid();
  }
}

// This function does roughly the same thing as GenerateThunk, but in a
// very different way, so that va_start and va_end work correctly.
// FIXME: This function assumes "this" is the first non-sret LLVM argument of
//        a function, and that there is an alloca built in the entry block
//        for all accesses to "this".
// FIXME: This function assumes there is only one "ret" statement per function.
// FIXME: Cloning isn't correct in the presence of indirect goto!
// FIXME: This implementation of thunks bloats codesize by duplicating the
//        function definition.  There are alternatives:
//        1. Add some sort of stub support to LLVM for cases where we can
//           do a this adjustment, then a sibcall.
//        2. We could transform the definition to take a va_list instead of an
//           actual variable argument list, then have the thunks (including a
//           no-op thunk for the regular definition) call va_start/va_end.
//           There's a bit of per-call overhead for this solution, but it's
//           better for codesize if the definition is long.
void CodeGenFunction::GenerateVarArgsThunk(
                                      llvm::Function *Fn,
                                      const CGFunctionInfo &FnInfo,
                                      GlobalDecl GD, const ThunkInfo &Thunk) {
  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
  QualType ResultType = FPT->getReturnType();

  // Get the original function
  assert(FnInfo.isVariadic());
  llvm::Type *Ty = CGM.getTypes().GetFunctionType(FnInfo);
  llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
  llvm::Function *BaseFn = cast<llvm::Function>(Callee);

  // Clone to thunk.
  llvm::ValueToValueMapTy VMap;
  llvm::Function *NewFn = llvm::CloneFunction(BaseFn, VMap,
                                              /*ModuleLevelChanges=*/false);
  CGM.getModule().getFunctionList().push_back(NewFn);
  Fn->replaceAllUsesWith(NewFn);
  NewFn->takeName(Fn);
  Fn->eraseFromParent();
  Fn = NewFn;

  // "Initialize" CGF (minimally).
  CurFn = Fn;

  // Get the "this" value
  llvm::Function::arg_iterator AI = Fn->arg_begin();
  if (CGM.ReturnTypeUsesSRet(FnInfo))
    ++AI;

  // Find the first store of "this", which will be to the alloca associated
  // with "this".
  llvm::Value *ThisPtr = &*AI;
  llvm::BasicBlock *EntryBB = Fn->begin();
  llvm::Instruction *ThisStore = 0;
  for (llvm::BasicBlock::iterator I = EntryBB->begin(), E = EntryBB->end();
       I != E; I++) {
    if (isa<llvm::StoreInst>(I) && I->getOperand(0) == ThisPtr) {
      ThisStore = cast<llvm::StoreInst>(I);
      break;
    }
  }
  assert(ThisStore && "Store of this should be in entry block?");
  // Adjust "this", if necessary.
  Builder.SetInsertPoint(ThisStore);
  llvm::Value *AdjustedThisPtr =
      CGM.getCXXABI().performThisAdjustment(*this, ThisPtr, Thunk.This);
  ThisStore->setOperand(0, AdjustedThisPtr);

  if (!Thunk.Return.isEmpty()) {
    // Fix up the returned value, if necessary.
    for (llvm::Function::iterator I = Fn->begin(), E = Fn->end(); I != E; I++) {
      llvm::Instruction *T = I->getTerminator();
      if (isa<llvm::ReturnInst>(T)) {
        RValue RV = RValue::get(T->getOperand(0));
        T->eraseFromParent();
        Builder.SetInsertPoint(&*I);
        RV = PerformReturnAdjustment(*this, ResultType, RV, Thunk);
        Builder.CreateRet(RV.getScalarVal());
        break;
      }
    }
  }
}

void CodeGenFunction::GenerateThunk(llvm::Function *Fn,
                                    const CGFunctionInfo &FnInfo,
                                    GlobalDecl GD, const ThunkInfo &Thunk) {
  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
  QualType ResultType = FPT->getResultType();
  QualType ThisType = MD->getThisType(getContext());

  FunctionArgList FunctionArgs;

  // FIXME: It would be nice if more of this code could be shared with 
  // CodeGenFunction::GenerateCode.

  // Create the implicit 'this' parameter declaration.
  CurGD = GD;
  CGM.getCXXABI().BuildInstanceFunctionParams(*this, ResultType, FunctionArgs);

  // Add the rest of the parameters.
  for (FunctionDecl::param_const_iterator I = MD->param_begin(),
       E = MD->param_end(); I != E; ++I) {
    ParmVarDecl *Param = *I;
    
    FunctionArgs.push_back(Param);
  }
  
  StartFunction(GlobalDecl(), ResultType, Fn, FnInfo, FunctionArgs,
                SourceLocation());

  CGM.getCXXABI().EmitInstanceFunctionProlog(*this);
  CXXThisValue = CXXABIThisValue;

  // Adjust the 'this' pointer if necessary.
  llvm::Value *AdjustedThisPtr = 
    PerformTypeAdjustment(*this, LoadCXXThis(), 
                          Thunk.This.NonVirtual, 
                          Thunk.This.VCallOffsetOffset,
                          /*IsReturnAdjustment*/false);
  
  CallArgList CallArgs;
  
  // Add our adjusted 'this' pointer.
  CallArgs.add(RValue::get(AdjustedThisPtr), ThisType);

  // Add the rest of the parameters.
  for (FunctionDecl::param_const_iterator I = MD->param_begin(),
       E = MD->param_end(); I != E; ++I) {
    ParmVarDecl *param = *I;
    EmitDelegateCallArg(CallArgs, param);
  }

  // Get our callee.
  llvm::Type *Ty =
    CGM.getTypes().GetFunctionType(CGM.getTypes().arrangeGlobalDeclaration(GD));
  llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);

#ifndef NDEBUG
  const CGFunctionInfo &CallFnInfo =
    CGM.getTypes().arrangeCXXMethodCall(CallArgs, FPT,
                                       RequiredArgs::forPrototypePlus(FPT, 1));
  assert(CallFnInfo.getRegParm() == FnInfo.getRegParm() &&
         CallFnInfo.isNoReturn() == FnInfo.isNoReturn() &&
         CallFnInfo.getCallingConvention() == FnInfo.getCallingConvention());
  assert(isa<CXXDestructorDecl>(MD) || // ignore dtor return types
         similar(CallFnInfo.getReturnInfo(), CallFnInfo.getReturnType(),
                 FnInfo.getReturnInfo(), FnInfo.getReturnType()));
  assert(CallFnInfo.arg_size() == FnInfo.arg_size());
  for (unsigned i = 0, e = FnInfo.arg_size(); i != e; ++i)
    assert(similar(CallFnInfo.arg_begin()[i].info,
                   CallFnInfo.arg_begin()[i].type,
                   FnInfo.arg_begin()[i].info, FnInfo.arg_begin()[i].type));
#endif
  
  // Determine whether we have a return value slot to use.
  ReturnValueSlot Slot;
  if (!ResultType->isVoidType() &&
      FnInfo.getReturnInfo().getKind() == ABIArgInfo::Indirect &&
      hasAggregateLLVMType(CurFnInfo->getReturnType()))
    Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified());
  
  // Now emit our call.
  RValue RV = EmitCall(FnInfo, Callee, Slot, CallArgs, MD);
  
  if (!Thunk.Return.isEmpty())
    RV = PerformReturnAdjustment(*this, ResultType, RV, Thunk);

  if (!ResultType->isVoidType() && Slot.isNull())
    CGM.getCXXABI().EmitReturnFromThunk(*this, RV, ResultType);

  // Disable the final ARC autorelease.
  AutoreleaseResult = false;

  FinishFunction();

  // Set the right linkage.
  CGM.setFunctionLinkage(MD, Fn);
  
  // Set the right visibility.
  setThunkVisibility(CGM, MD, Thunk, Fn);
}

RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
                                 llvm::Value *Callee,
                                 const CallArgList &CallArgs,
                                 const Decl *TargetDecl) {
  // FIXME: We no longer need the types from CallArgs; lift up and simplify.
  llvm::SmallVector<llvm::Value*, 16> Args;

  // Handle struct-return functions by passing a pointer to the
  // location that we would like to return into.
  QualType RetTy = CallInfo.getReturnType();
  const ABIArgInfo &RetAI = CallInfo.getReturnInfo();


  // If the call returns a temporary with struct return, create a temporary
  // alloca to hold the result.
  if (CGM.ReturnTypeUsesSret(CallInfo))
    Args.push_back(CreateTempAlloca(ConvertTypeForMem(RetTy)));

  assert(CallInfo.arg_size() == CallArgs.size() &&
         "Mismatch between function signature & arguments.");
  CGFunctionInfo::const_arg_iterator info_it = CallInfo.arg_begin();
  for (CallArgList::const_iterator I = CallArgs.begin(), E = CallArgs.end();
       I != E; ++I, ++info_it) {
    const ABIArgInfo &ArgInfo = info_it->info;
    RValue RV = I->first;

    switch (ArgInfo.getKind()) {
    case ABIArgInfo::Indirect:
      if (RV.isScalar() || RV.isComplex()) {
        // Make a temporary alloca to pass the argument.
        Args.push_back(CreateTempAlloca(ConvertTypeForMem(I->second)));
        if (RV.isScalar())
          EmitStoreOfScalar(RV.getScalarVal(), Args.back(), false, I->second);
        else
          StoreComplexToAddr(RV.getComplexVal(), Args.back(), false);
      } else {
        Args.push_back(RV.getAggregateAddr());
      }
      break;

    case ABIArgInfo::Extend:
    case ABIArgInfo::Direct:
      if (RV.isScalar()) {
        Args.push_back(RV.getScalarVal());
      } else if (RV.isComplex()) {
        llvm::Value *Tmp = llvm::UndefValue::get(ConvertType(I->second));
        Tmp = Builder.CreateInsertValue(Tmp, RV.getComplexVal().first, 0);
        Tmp = Builder.CreateInsertValue(Tmp, RV.getComplexVal().second, 1);
        Args.push_back(Tmp);
      } else {
        Args.push_back(Builder.CreateLoad(RV.getAggregateAddr()));
      }
      break;

    case ABIArgInfo::Ignore:
      break;

    case ABIArgInfo::Coerce: {
      // FIXME: Avoid the conversion through memory if possible.
      llvm::Value *SrcPtr;
      if (RV.isScalar()) {
        SrcPtr = CreateTempAlloca(ConvertTypeForMem(I->second), "coerce");
        EmitStoreOfScalar(RV.getScalarVal(), SrcPtr, false, I->second);
      } else if (RV.isComplex()) {
        SrcPtr = CreateTempAlloca(ConvertTypeForMem(I->second), "coerce");
        StoreComplexToAddr(RV.getComplexVal(), SrcPtr, false);
      } else
        SrcPtr = RV.getAggregateAddr();
      Args.push_back(CreateCoercedLoad(SrcPtr, ArgInfo.getCoerceToType(),
                                       *this));
      break;
    }

    case ABIArgInfo::Expand:
      ExpandTypeToArgs(I->second, RV, Args);
      break;
    }
  }

  // If the callee is a bitcast of a function to a varargs pointer to function
  // type, check to see if we can remove the bitcast.  This handles some cases
  // with unprototyped functions.
  if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(Callee))
    if (llvm::Function *CalleeF = dyn_cast<llvm::Function>(CE->getOperand(0))) {
      const llvm::PointerType *CurPT=cast<llvm::PointerType>(Callee->getType());
      const llvm::FunctionType *CurFT =
        cast<llvm::FunctionType>(CurPT->getElementType());
      const llvm::FunctionType *ActualFT = CalleeF->getFunctionType();

      if (CE->getOpcode() == llvm::Instruction::BitCast &&
          ActualFT->getReturnType() == CurFT->getReturnType() &&
          ActualFT->getNumParams() == CurFT->getNumParams() &&
          ActualFT->getNumParams() == Args.size()) {
        bool ArgsMatch = true;
        for (unsigned i = 0, e = ActualFT->getNumParams(); i != e; ++i)
          if (ActualFT->getParamType(i) != CurFT->getParamType(i)) {
            ArgsMatch = false;
            break;
          }

//.........这里部分代码省略.........

void CodeGenModule::ConstructAttributeList(const CGFunctionInfo &FI,
                                           const Decl *TargetDecl,
                                           AttributeListType &PAL, 
                                           unsigned &CallingConv) {
  unsigned FuncAttrs = 0;
  unsigned RetAttrs = 0;

  CallingConv = FI.getEffectiveCallingConvention();

  // FIXME: handle sseregparm someday...
  if (TargetDecl) {
    if (TargetDecl->hasAttr<NoThrowAttr>())
      FuncAttrs |= llvm::Attribute::NoUnwind;
    if (TargetDecl->hasAttr<NoReturnAttr>())
      FuncAttrs |= llvm::Attribute::NoReturn;
    if (TargetDecl->hasAttr<ConstAttr>())
      FuncAttrs |= llvm::Attribute::ReadNone;
    else if (TargetDecl->hasAttr<PureAttr>())
      FuncAttrs |= llvm::Attribute::ReadOnly;
    if (TargetDecl->hasAttr<MallocAttr>())
      RetAttrs |= llvm::Attribute::NoAlias;
  }

  if (CodeGenOpts.OptimizeSize)
    FuncAttrs |= llvm::Attribute::OptimizeForSize;
  if (CodeGenOpts.DisableRedZone)
    FuncAttrs |= llvm::Attribute::NoRedZone;
  if (CodeGenOpts.NoImplicitFloat)
    FuncAttrs |= llvm::Attribute::NoImplicitFloat;

  QualType RetTy = FI.getReturnType();
  unsigned Index = 1;
  const ABIArgInfo &RetAI = FI.getReturnInfo();
  switch (RetAI.getKind()) {
  case ABIArgInfo::Extend:
   if (RetTy->isSignedIntegerType()) {
     RetAttrs |= llvm::Attribute::SExt;
   } else if (RetTy->isUnsignedIntegerType()) {
     RetAttrs |= llvm::Attribute::ZExt;
   }
   // FALLTHROUGH
  case ABIArgInfo::Direct:
    break;

  case ABIArgInfo::Indirect:
    PAL.push_back(llvm::AttributeWithIndex::get(Index,
                                                llvm::Attribute::StructRet |
                                                llvm::Attribute::NoAlias));
    ++Index;
    // sret disables readnone and readonly
    FuncAttrs &= ~(llvm::Attribute::ReadOnly |
                   llvm::Attribute::ReadNone);
    break;

  case ABIArgInfo::Ignore:
  case ABIArgInfo::Coerce:
    break;

  case ABIArgInfo::Expand:
    assert(0 && "Invalid ABI kind for return argument");
  }

  if (RetAttrs)
    PAL.push_back(llvm::AttributeWithIndex::get(0, RetAttrs));

  // FIXME: we need to honour command line settings also...
  // FIXME: RegParm should be reduced in case of nested functions and/or global
  // register variable.
  signed RegParm = 0;
  if (TargetDecl)
    if (const RegparmAttr *RegParmAttr
          = TargetDecl->getAttr<RegparmAttr>())
      RegParm = RegParmAttr->getNumParams();

  unsigned PointerWidth = getContext().Target.getPointerWidth(0);
  for (CGFunctionInfo::const_arg_iterator it = FI.arg_begin(),
         ie = FI.arg_end(); it != ie; ++it) {
    QualType ParamType = it->type;
    const ABIArgInfo &AI = it->info;
    unsigned Attributes = 0;

    switch (AI.getKind()) {
    case ABIArgInfo::Coerce:
      break;

    case ABIArgInfo::Indirect:
      if (AI.getIndirectByVal())
        Attributes |= llvm::Attribute::ByVal;

      Attributes |=
        llvm::Attribute::constructAlignmentFromInt(AI.getIndirectAlign());
      // byval disables readnone and readonly.
      FuncAttrs &= ~(llvm::Attribute::ReadOnly |
                     llvm::Attribute::ReadNone);
      break;

    case ABIArgInfo::Extend:
     if (ParamType->isSignedIntegerType()) {
       Attributes |= llvm::Attribute::SExt;
     } else if (ParamType->isUnsignedIntegerType()) {
//.........这里部分代码省略.........

bool CodeGenModule::ReturnTypeUsesSret(const CGFunctionInfo &FI) {
  return FI.getReturnInfo().isIndirect();
}