C++ CGFunctionInfo::arg_begin方法代码示例

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);
}

void CodeGenFunction::EmitFunctionProlog(const CGFunctionInfo &FI,
                                         llvm::Function *Fn,
                                         const FunctionArgList &Args) {
  // If this is an implicit-return-zero function, go ahead and
  // initialize the return value.  TODO: it might be nice to have
  // a more general mechanism for this that didn't require synthesized
  // return statements.
  if (const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(CurFuncDecl)) {
    if (FD->hasImplicitReturnZero()) {
      QualType RetTy = FD->getResultType().getUnqualifiedType();
      const llvm::Type* LLVMTy = CGM.getTypes().ConvertType(RetTy);
      llvm::Constant* Zero = llvm::Constant::getNullValue(LLVMTy);
      Builder.CreateStore(Zero, ReturnValue);
    }
  }

  // FIXME: We no longer need the types from FunctionArgList; lift up and
  // simplify.

  // Emit allocs for param decls.  Give the LLVM Argument nodes names.
  llvm::Function::arg_iterator AI = Fn->arg_begin();

  // Name the struct return argument.
  if (CGM.ReturnTypeUsesSret(FI)) {
    AI->setName("agg.result");
    ++AI;
  }

  assert(FI.arg_size() == Args.size() &&
         "Mismatch between function signature & arguments.");
  CGFunctionInfo::const_arg_iterator info_it = FI.arg_begin();
  for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
       i != e; ++i, ++info_it) {
    const VarDecl *Arg = i->first;
    QualType Ty = info_it->type;
    const ABIArgInfo &ArgI = info_it->info;

    switch (ArgI.getKind()) {
    case ABIArgInfo::Indirect: {
      llvm::Value* V = AI;
      if (hasAggregateLLVMType(Ty)) {
        // Do nothing, aggregates and complex variables are accessed by
        // reference.
      } else {
        // Load scalar value from indirect argument.
        V = EmitLoadOfScalar(V, false, Ty);
        if (!getContext().typesAreCompatible(Ty, Arg->getType())) {
          // This must be a promotion, for something like
          // "void a(x) short x; {..."
          V = EmitScalarConversion(V, Ty, Arg->getType());
        }
      }
      EmitParmDecl(*Arg, V);
      break;
    }

    case ABIArgInfo::Extend:
    case ABIArgInfo::Direct: {
      assert(AI != Fn->arg_end() && "Argument mismatch!");
      llvm::Value* V = AI;
      if (hasAggregateLLVMType(Ty)) {
        // Create a temporary alloca to hold the argument; the rest of
        // codegen expects to access aggregates & complex values by
        // reference.
        V = CreateTempAlloca(ConvertTypeForMem(Ty));
        Builder.CreateStore(AI, V);
      } else {
        if (!getContext().typesAreCompatible(Ty, Arg->getType())) {
          // This must be a promotion, for something like
          // "void a(x) short x; {..."
          V = EmitScalarConversion(V, Ty, Arg->getType());
        }
      }
      EmitParmDecl(*Arg, V);
      break;
    }

    case ABIArgInfo::Expand: {
      // If this structure was expanded into multiple arguments then
      // we need to create a temporary and reconstruct it from the
      // arguments.
      llvm::Value *Temp = CreateTempAlloca(ConvertTypeForMem(Ty),
                                           Arg->getName() + ".addr");
      // FIXME: What are the right qualifiers here?
      llvm::Function::arg_iterator End =
        ExpandTypeFromArgs(Ty, LValue::MakeAddr(Temp, Qualifiers()), AI);
      EmitParmDecl(*Arg, Temp);

      // Name the arguments used in expansion and increment AI.
      unsigned Index = 0;
      for (; AI != End; ++AI, ++Index)
        AI->setName(Arg->getName() + "." + llvm::Twine(Index));
      continue;
    }

    case ABIArgInfo::Ignore:
      // Initialize the local variable appropriately.
      if (hasAggregateLLVMType(Ty)) {
        EmitParmDecl(*Arg, CreateTempAlloca(ConvertTypeForMem(Ty)));
      } else {
//.........这里部分代码省略.........

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.........