[lldb][NFC] Refactor _get_bool_config_skip_if_decorator

[lldb.git] / clang / lib / CodeGen / CGCall.cpp

//===--- CGCall.cpp - Encapsulate calling convention details --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// These classes wrap the information about a call or function
// definition used to handle ABI compliancy.
//
//===----------------------------------------------------------------------===//

#include "CGCall.h"
#include "ABIInfo.h"
#include "CGBlocks.h"
#include "CGCXXABI.h"
#include "CGCleanup.h"
#include "CGRecordLayout.h"
#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include "TargetInfo.h"
#include "clang/AST/Attr.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/Basic/CodeGenOptions.h"
#include "clang/Basic/TargetBuiltins.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/CodeGen/CGFunctionInfo.h"
#include "clang/CodeGen/SwiftCallingConv.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace clang;
using namespace CodeGen;

/***/

unsigned CodeGenTypes::ClangCallConvToLLVMCallConv(CallingConv CC) {
  switch (CC) {
  default: return llvm::CallingConv::C;
  case CC_X86StdCall: return llvm::CallingConv::X86_StdCall;
  case CC_X86FastCall: return llvm::CallingConv::X86_FastCall;
  case CC_X86RegCall: return llvm::CallingConv::X86_RegCall;
  case CC_X86ThisCall: return llvm::CallingConv::X86_ThisCall;
  case CC_Win64: return llvm::CallingConv::Win64;
  case CC_X86_64SysV: return llvm::CallingConv::X86_64_SysV;
  case CC_AAPCS: return llvm::CallingConv::ARM_AAPCS;
  case CC_AAPCS_VFP: return llvm::CallingConv::ARM_AAPCS_VFP;
  case CC_IntelOclBicc: return llvm::CallingConv::Intel_OCL_BI;
  // TODO: Add support for __pascal to LLVM.
  case CC_X86Pascal: return llvm::CallingConv::C;
  // TODO: Add support for __vectorcall to LLVM.
  case CC_X86VectorCall: return llvm::CallingConv::X86_VectorCall;
  case CC_AArch64VectorCall: return llvm::CallingConv::AArch64_VectorCall;
  case CC_SpirFunction: return llvm::CallingConv::SPIR_FUNC;
  case CC_OpenCLKernel: return CGM.getTargetCodeGenInfo().getOpenCLKernelCallingConv();
  case CC_PreserveMost: return llvm::CallingConv::PreserveMost;
  case CC_PreserveAll: return llvm::CallingConv::PreserveAll;
  case CC_Swift: return llvm::CallingConv::Swift;
  }
}

/// Derives the 'this' type for codegen purposes, i.e. ignoring method CVR
/// qualification. Either or both of RD and MD may be null. A null RD indicates
/// that there is no meaningful 'this' type, and a null MD can occur when
/// calling a method pointer.
CanQualType CodeGenTypes::DeriveThisType(const CXXRecordDecl *RD,
                                         const CXXMethodDecl *MD) {
  QualType RecTy;
  if (RD)
    RecTy = Context.getTagDeclType(RD)->getCanonicalTypeInternal();
  else
    RecTy = Context.VoidTy;

  if (MD)
    RecTy = Context.getAddrSpaceQualType(RecTy, MD->getMethodQualifiers().getAddressSpace());
  return Context.getPointerType(CanQualType::CreateUnsafe(RecTy));
}

/// Returns the canonical formal type of the given C++ method.
static CanQual<FunctionProtoType> GetFormalType(const CXXMethodDecl *MD) {
  return MD->getType()->getCanonicalTypeUnqualified()
           .getAs<FunctionProtoType>();
}

/// Returns the "extra-canonicalized" return type, which discards
/// qualifiers on the return type.  Codegen doesn't care about them,
/// and it makes ABI code a little easier to be able to assume that
/// all parameter and return types are top-level unqualified.
static CanQualType GetReturnType(QualType RetTy) {
  return RetTy->getCanonicalTypeUnqualified().getUnqualifiedType();
}

/// Arrange the argument and result information for a value of the given
/// unprototyped freestanding function type.
const CGFunctionInfo &
CodeGenTypes::arrangeFreeFunctionType(CanQual<FunctionNoProtoType> FTNP) {
  // When translating an unprototyped function type, always use a
  // variadic type.
  return arrangeLLVMFunctionInfo(FTNP->getReturnType().getUnqualifiedType(),
                                 /*instanceMethod=*/false,
                                 /*chainCall=*/false, None,
                                 FTNP->getExtInfo(), {}, RequiredArgs(0));
}

static void addExtParameterInfosForCall(
         llvm::SmallVectorImpl<FunctionProtoType::ExtParameterInfo> &paramInfos,
                                        const FunctionProtoType *proto,
                                        unsigned prefixArgs,
                                        unsigned totalArgs) {
  assert(proto->hasExtParameterInfos());
  assert(paramInfos.size() <= prefixArgs);
  assert(proto->getNumParams() + prefixArgs <= totalArgs);

  paramInfos.reserve(totalArgs);

  // Add default infos for any prefix args that don't already have infos.
  paramInfos.resize(prefixArgs);

  // Add infos for the prototype.
  for (const auto &ParamInfo : proto->getExtParameterInfos()) {
    paramInfos.push_back(ParamInfo);
    // pass_object_size params have no parameter info.
    if (ParamInfo.hasPassObjectSize())
      paramInfos.emplace_back();
  }

  assert(paramInfos.size() <= totalArgs &&
         "Did we forget to insert pass_object_size args?");
  // Add default infos for the variadic and/or suffix arguments.
  paramInfos.resize(totalArgs);
}

/// Adds the formal parameters in FPT to the given prefix. If any parameter in
/// FPT has pass_object_size attrs, then we'll add parameters for those, too.
static void appendParameterTypes(const CodeGenTypes &CGT,
                                 SmallVectorImpl<CanQualType> &prefix,
              SmallVectorImpl<FunctionProtoType::ExtParameterInfo> &paramInfos,
                                 CanQual<FunctionProtoType> FPT) {
  // Fast path: don't touch param info if we don't need to.
  if (!FPT->hasExtParameterInfos()) {
    assert(paramInfos.empty() &&
           "We have paramInfos, but the prototype doesn't?");
    prefix.append(FPT->param_type_begin(), FPT->param_type_end());
    return;
  }

  unsigned PrefixSize = prefix.size();
  // In the vast majority of cases, we'll have precisely FPT->getNumParams()
  // parameters; the only thing that can change this is the presence of
  // pass_object_size. So, we preallocate for the common case.
  prefix.reserve(prefix.size() + FPT->getNumParams());

  auto ExtInfos = FPT->getExtParameterInfos();
  assert(ExtInfos.size() == FPT->getNumParams());
  for (unsigned I = 0, E = FPT->getNumParams(); I != E; ++I) {
    prefix.push_back(FPT->getParamType(I));
    if (ExtInfos[I].hasPassObjectSize())
      prefix.push_back(CGT.getContext().getSizeType());
  }

  addExtParameterInfosForCall(paramInfos, FPT.getTypePtr(), PrefixSize,
                              prefix.size());
}

/// Arrange the LLVM function layout for a value of the given function
/// type, on top of any implicit parameters already stored.
static const CGFunctionInfo &
arrangeLLVMFunctionInfo(CodeGenTypes &CGT, bool instanceMethod,
                        SmallVectorImpl<CanQualType> &prefix,
                        CanQual<FunctionProtoType> FTP) {
  SmallVector<FunctionProtoType::ExtParameterInfo, 16> paramInfos;
  RequiredArgs Required = RequiredArgs::forPrototypePlus(FTP, prefix.size());
  // FIXME: Kill copy.
  appendParameterTypes(CGT, prefix, paramInfos, FTP);
  CanQualType resultType = FTP->getReturnType().getUnqualifiedType();

  return CGT.arrangeLLVMFunctionInfo(resultType, instanceMethod,
                                     /*chainCall=*/false, prefix,
                                     FTP->getExtInfo(), paramInfos,
                                     Required);
}

/// Arrange the argument and result information for a value of the
/// given freestanding function type.
const CGFunctionInfo &
CodeGenTypes::arrangeFreeFunctionType(CanQual<FunctionProtoType> FTP) {
  SmallVector<CanQualType, 16> argTypes;
  return ::arrangeLLVMFunctionInfo(*this, /*instanceMethod=*/false, argTypes,
                                   FTP);
}

static CallingConv getCallingConventionForDecl(const Decl *D, bool IsWindows) {
  // Set the appropriate calling convention for the Function.
  if (D->hasAttr<StdCallAttr>())
    return CC_X86StdCall;

  if (D->hasAttr<FastCallAttr>())
    return CC_X86FastCall;

  if (D->hasAttr<RegCallAttr>())
    return CC_X86RegCall;

  if (D->hasAttr<ThisCallAttr>())
    return CC_X86ThisCall;

  if (D->hasAttr<VectorCallAttr>())
    return CC_X86VectorCall;

  if (D->hasAttr<PascalAttr>())
    return CC_X86Pascal;

  if (PcsAttr *PCS = D->getAttr<PcsAttr>())
    return (PCS->getPCS() == PcsAttr::AAPCS ? CC_AAPCS : CC_AAPCS_VFP);

  if (D->hasAttr<AArch64VectorPcsAttr>())
    return CC_AArch64VectorCall;

  if (D->hasAttr<IntelOclBiccAttr>())
    return CC_IntelOclBicc;

  if (D->hasAttr<MSABIAttr>())
    return IsWindows ? CC_C : CC_Win64;

  if (D->hasAttr<SysVABIAttr>())
    return IsWindows ? CC_X86_64SysV : CC_C;

  if (D->hasAttr<PreserveMostAttr>())
    return CC_PreserveMost;

  if (D->hasAttr<PreserveAllAttr>())
    return CC_PreserveAll;

  return CC_C;
}

/// Arrange the argument and result information for a call to an
/// unknown C++ non-static member function of the given abstract type.
/// (A null RD means we don't have any meaningful "this" argument type,
///  so fall back to a generic pointer type).
/// The member function must be an ordinary function, i.e. not a
/// constructor or destructor.
const CGFunctionInfo &
CodeGenTypes::arrangeCXXMethodType(const CXXRecordDecl *RD,
                                   const FunctionProtoType *FTP,
                                   const CXXMethodDecl *MD) {
  SmallVector<CanQualType, 16> argTypes;

  // Add the 'this' pointer.
  argTypes.push_back(DeriveThisType(RD, MD));

  return ::arrangeLLVMFunctionInfo(
      *this, true, argTypes,
      FTP->getCanonicalTypeUnqualified().getAs<FunctionProtoType>());
}

/// Set calling convention for CUDA/HIP kernel.
static void setCUDAKernelCallingConvention(CanQualType &FTy, CodeGenModule &CGM,
                                           const FunctionDecl *FD) {
  if (FD->hasAttr<CUDAGlobalAttr>()) {
    const FunctionType *FT = FTy->getAs<FunctionType>();
    CGM.getTargetCodeGenInfo().setCUDAKernelCallingConvention(FT);
    FTy = FT->getCanonicalTypeUnqualified();
  }
}

/// Arrange the argument and result information for a declaration or
/// definition of the given C++ non-static member function.  The
/// member function must be an ordinary function, i.e. not a
/// constructor or destructor.
const CGFunctionInfo &
CodeGenTypes::arrangeCXXMethodDeclaration(const CXXMethodDecl *MD) {
  assert(!isa<CXXConstructorDecl>(MD) && "wrong method for constructors!");
  assert(!isa<CXXDestructorDecl>(MD) && "wrong method for destructors!");

  CanQualType FT = GetFormalType(MD).getAs<Type>();
  setCUDAKernelCallingConvention(FT, CGM, MD);
  auto prototype = FT.getAs<FunctionProtoType>();

  if (MD->isInstance()) {
    // The abstract case is perfectly fine.
    const CXXRecordDecl *ThisType = TheCXXABI.getThisArgumentTypeForMethod(MD);
    return arrangeCXXMethodType(ThisType, prototype.getTypePtr(), MD);
  }

  return arrangeFreeFunctionType(prototype);
}

bool CodeGenTypes::inheritingCtorHasParams(
    const InheritedConstructor &Inherited, CXXCtorType Type) {
  // Parameters are unnecessary if we're constructing a base class subobject
  // and the inherited constructor lives in a virtual base.
  return Type == Ctor_Complete ||
         !Inherited.getShadowDecl()->constructsVirtualBase() ||
         !Target.getCXXABI().hasConstructorVariants();
}

const CGFunctionInfo &
CodeGenTypes::arrangeCXXStructorDeclaration(GlobalDecl GD) {
  auto *MD = cast<CXXMethodDecl>(GD.getDecl());

  SmallVector<CanQualType, 16> argTypes;
  SmallVector<FunctionProtoType::ExtParameterInfo, 16> paramInfos;
  argTypes.push_back(DeriveThisType(MD->getParent(), MD));

  bool PassParams = true;

  if (auto *CD = dyn_cast<CXXConstructorDecl>(MD)) {
    // A base class inheriting constructor doesn't get forwarded arguments
    // needed to construct a virtual base (or base class thereof).
    if (auto Inherited = CD->getInheritedConstructor())
      PassParams = inheritingCtorHasParams(Inherited, GD.getCtorType());
  }

  CanQual<FunctionProtoType> FTP = GetFormalType(MD);

  // Add the formal parameters.
  if (PassParams)
    appendParameterTypes(*this, argTypes, paramInfos, FTP);

  CGCXXABI::AddedStructorArgCounts AddedArgs =
      TheCXXABI.buildStructorSignature(GD, argTypes);
  if (!paramInfos.empty()) {
    // Note: prefix implies after the first param.
    if (AddedArgs.Prefix)
      paramInfos.insert(paramInfos.begin() + 1, AddedArgs.Prefix,
                        FunctionProtoType::ExtParameterInfo{});
    if (AddedArgs.Suffix)
      paramInfos.append(AddedArgs.Suffix,
                        FunctionProtoType::ExtParameterInfo{});
  }

  RequiredArgs required =
      (PassParams && MD->isVariadic() ? RequiredArgs(argTypes.size())
                                      : RequiredArgs::All);

  FunctionType::ExtInfo extInfo = FTP->getExtInfo();
  CanQualType resultType = TheCXXABI.HasThisReturn(GD)
                               ? argTypes.front()
                               : TheCXXABI.hasMostDerivedReturn(GD)
                                     ? CGM.getContext().VoidPtrTy
                                     : Context.VoidTy;
  return arrangeLLVMFunctionInfo(resultType, /*instanceMethod=*/true,
                                 /*chainCall=*/false, argTypes, extInfo,
                                 paramInfos, required);
}

static SmallVector<CanQualType, 16>
getArgTypesForCall(ASTContext &ctx, const CallArgList &args) {
  SmallVector<CanQualType, 16> argTypes;
  for (auto &arg : args)
    argTypes.push_back(ctx.getCanonicalParamType(arg.Ty));
  return argTypes;
}

static SmallVector<CanQualType, 16>
getArgTypesForDeclaration(ASTContext &ctx, const FunctionArgList &args) {
  SmallVector<CanQualType, 16> argTypes;
  for (auto &arg : args)
    argTypes.push_back(ctx.getCanonicalParamType(arg->getType()));
  return argTypes;
}

static llvm::SmallVector<FunctionProtoType::ExtParameterInfo, 16>
getExtParameterInfosForCall(const FunctionProtoType *proto,
                            unsigned prefixArgs, unsigned totalArgs) {
  llvm::SmallVector<FunctionProtoType::ExtParameterInfo, 16> result;
  if (proto->hasExtParameterInfos()) {
    addExtParameterInfosForCall(result, proto, prefixArgs, totalArgs);
  }
  return result;
}

/// Arrange a call to a C++ method, passing the given arguments.
///
/// ExtraPrefixArgs is the number of ABI-specific args passed after the `this`
/// parameter.
/// ExtraSuffixArgs is the number of ABI-specific args passed at the end of
/// args.
/// PassProtoArgs indicates whether `args` has args for the parameters in the
/// given CXXConstructorDecl.
const CGFunctionInfo &
CodeGenTypes::arrangeCXXConstructorCall(const CallArgList &args,
                                        const CXXConstructorDecl *D,
                                        CXXCtorType CtorKind,
                                        unsigned ExtraPrefixArgs,
                                        unsigned ExtraSuffixArgs,
                                        bool PassProtoArgs) {
  // FIXME: Kill copy.
  SmallVector<CanQualType, 16> ArgTypes;
  for (const auto &Arg : args)
    ArgTypes.push_back(Context.getCanonicalParamType(Arg.Ty));

  // +1 for implicit this, which should always be args[0].
  unsigned TotalPrefixArgs = 1 + ExtraPrefixArgs;

  CanQual<FunctionProtoType> FPT = GetFormalType(D);
  RequiredArgs Required = PassProtoArgs
                              ? RequiredArgs::forPrototypePlus(
                                    FPT, TotalPrefixArgs + ExtraSuffixArgs)
                              : RequiredArgs::All;

  GlobalDecl GD(D, CtorKind);
  CanQualType ResultType = TheCXXABI.HasThisReturn(GD)
                               ? ArgTypes.front()
                               : TheCXXABI.hasMostDerivedReturn(GD)
                                     ? CGM.getContext().VoidPtrTy
                                     : Context.VoidTy;

  FunctionType::ExtInfo Info = FPT->getExtInfo();
  llvm::SmallVector<FunctionProtoType::ExtParameterInfo, 16> ParamInfos;
  // If the prototype args are elided, we should only have ABI-specific args,
  // which never have param info.
  if (PassProtoArgs && FPT->hasExtParameterInfos()) {
    // ABI-specific suffix arguments are treated the same as variadic arguments.
    addExtParameterInfosForCall(ParamInfos, FPT.getTypePtr(), TotalPrefixArgs,
                                ArgTypes.size());
  }
  return arrangeLLVMFunctionInfo(ResultType, /*instanceMethod=*/true,
                                 /*chainCall=*/false, ArgTypes, Info,
                                 ParamInfos, Required);
}

/// Arrange the argument and result information for the declaration or
/// definition of the given function.
const CGFunctionInfo &
CodeGenTypes::arrangeFunctionDeclaration(const FunctionDecl *FD) {
  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD))
    if (MD->isInstance())
      return arrangeCXXMethodDeclaration(MD);

  CanQualType FTy = FD->getType()->getCanonicalTypeUnqualified();

  assert(isa<FunctionType>(FTy));
  setCUDAKernelCallingConvention(FTy, CGM, FD);

  // When declaring a function without a prototype, always use a
  // non-variadic type.
  if (CanQual<FunctionNoProtoType> noProto = FTy.getAs<FunctionNoProtoType>()) {
    return arrangeLLVMFunctionInfo(
        noProto->getReturnType(), /*instanceMethod=*/false,
        /*chainCall=*/false, None, noProto->getExtInfo(), {},RequiredArgs::All);
  }

  return arrangeFreeFunctionType(FTy.castAs<FunctionProtoType>());
}

/// Arrange the argument and result information for the declaration or
/// definition of an Objective-C method.
const CGFunctionInfo &
CodeGenTypes::arrangeObjCMethodDeclaration(const ObjCMethodDecl *MD) {
  // It happens that this is the same as a call with no optional
  // arguments, except also using the formal 'self' type.
  return arrangeObjCMessageSendSignature(MD, MD->getSelfDecl()->getType());
}

/// Arrange the argument and result information for the function type
/// through which to perform a send to the given Objective-C method,
/// using the given receiver type.  The receiver type is not always
/// the 'self' type of the method or even an Objective-C pointer type.
/// This is *not* the right method for actually performing such a
/// message send, due to the possibility of optional arguments.
const CGFunctionInfo &
CodeGenTypes::arrangeObjCMessageSendSignature(const ObjCMethodDecl *MD,
                                              QualType receiverType) {
  SmallVector<CanQualType, 16> argTys;
  SmallVector<FunctionProtoType::ExtParameterInfo, 4> extParamInfos(2);
  argTys.push_back(Context.getCanonicalParamType(receiverType));
  argTys.push_back(Context.getCanonicalParamType(Context.getObjCSelType()));
  // FIXME: Kill copy?
  for (const auto *I : MD->parameters()) {
    argTys.push_back(Context.getCanonicalParamType(I->getType()));
    auto extParamInfo = FunctionProtoType::ExtParameterInfo().withIsNoEscape(
        I->hasAttr<NoEscapeAttr>());
    extParamInfos.push_back(extParamInfo);
  }

  FunctionType::ExtInfo einfo;
  bool IsWindows = getContext().getTargetInfo().getTriple().isOSWindows();
  einfo = einfo.withCallingConv(getCallingConventionForDecl(MD, IsWindows));

  if (getContext().getLangOpts().ObjCAutoRefCount &&
      MD->hasAttr<NSReturnsRetainedAttr>())
    einfo = einfo.withProducesResult(true);

  RequiredArgs required =
    (MD->isVariadic() ? RequiredArgs(argTys.size()) : RequiredArgs::All);

  return arrangeLLVMFunctionInfo(
      GetReturnType(MD->getReturnType()), /*instanceMethod=*/false,
      /*chainCall=*/false, argTys, einfo, extParamInfos, required);
}

const CGFunctionInfo &
CodeGenTypes::arrangeUnprototypedObjCMessageSend(QualType returnType,
                                                 const CallArgList &args) {
  auto argTypes = getArgTypesForCall(Context, args);
  FunctionType::ExtInfo einfo;

  return arrangeLLVMFunctionInfo(
      GetReturnType(returnType), /*instanceMethod=*/false,
      /*chainCall=*/false, argTypes, einfo, {}, RequiredArgs::All);
}

const CGFunctionInfo &
CodeGenTypes::arrangeGlobalDeclaration(GlobalDecl GD) {
  // FIXME: Do we need to handle ObjCMethodDecl?
  const FunctionDecl *FD = cast<FunctionDecl>(GD.getDecl());

  if (isa<CXXConstructorDecl>(GD.getDecl()) ||
      isa<CXXDestructorDecl>(GD.getDecl()))
    return arrangeCXXStructorDeclaration(GD);

  return arrangeFunctionDeclaration(FD);
}

/// Arrange a thunk that takes 'this' as the first parameter followed by
/// varargs.  Return a void pointer, regardless of the actual return type.
/// The body of the thunk will end in a musttail call to a function of the
/// correct type, and the caller will bitcast the function to the correct
/// prototype.
const CGFunctionInfo &
CodeGenTypes::arrangeUnprototypedMustTailThunk(const CXXMethodDecl *MD) {
  assert(MD->isVirtual() && "only methods have thunks");
  CanQual<FunctionProtoType> FTP = GetFormalType(MD);
  CanQualType ArgTys[] = {DeriveThisType(MD->getParent(), MD)};
  return arrangeLLVMFunctionInfo(Context.VoidTy, /*instanceMethod=*/false,
                                 /*chainCall=*/false, ArgTys,
                                 FTP->getExtInfo(), {}, RequiredArgs(1));
}

const CGFunctionInfo &
CodeGenTypes::arrangeMSCtorClosure(const CXXConstructorDecl *CD,
                                   CXXCtorType CT) {
  assert(CT == Ctor_CopyingClosure || CT == Ctor_DefaultClosure);

  CanQual<FunctionProtoType> FTP = GetFormalType(CD);
  SmallVector<CanQualType, 2> ArgTys;
  const CXXRecordDecl *RD = CD->getParent();
  ArgTys.push_back(DeriveThisType(RD, CD));
  if (CT == Ctor_CopyingClosure)
    ArgTys.push_back(*FTP->param_type_begin());
  if (RD->getNumVBases() > 0)
    ArgTys.push_back(Context.IntTy);
  CallingConv CC = Context.getDefaultCallingConvention(
      /*IsVariadic=*/false, /*IsCXXMethod=*/true);
  return arrangeLLVMFunctionInfo(Context.VoidTy, /*instanceMethod=*/true,
                                 /*chainCall=*/false, ArgTys,
                                 FunctionType::ExtInfo(CC), {},
                                 RequiredArgs::All);
}

/// Arrange a call as unto a free function, except possibly with an
/// additional number of formal parameters considered required.
static const CGFunctionInfo &
arrangeFreeFunctionLikeCall(CodeGenTypes &CGT,
                            CodeGenModule &CGM,
                            const CallArgList &args,
                            const FunctionType *fnType,
                            unsigned numExtraRequiredArgs,
                            bool chainCall) {
  assert(args.size() >= numExtraRequiredArgs);

  llvm::SmallVector<FunctionProtoType::ExtParameterInfo, 16> paramInfos;

  // In most cases, there are no optional arguments.
  RequiredArgs required = RequiredArgs::All;

  // If we have a variadic prototype, the required arguments are the
  // extra prefix plus the arguments in the prototype.
  if (const FunctionProtoType *proto = dyn_cast<FunctionProtoType>(fnType)) {
    if (proto->isVariadic())
      required = RequiredArgs::forPrototypePlus(proto, numExtraRequiredArgs);

    if (proto->hasExtParameterInfos())
      addExtParameterInfosForCall(paramInfos, proto, numExtraRequiredArgs,
                                  args.size());

  // If we don't have a prototype at all, but we're supposed to
  // explicitly use the variadic convention for unprototyped calls,
  // treat all of the arguments as required but preserve the nominal
  // possibility of variadics.
  } else if (CGM.getTargetCodeGenInfo()
                .isNoProtoCallVariadic(args,
                                       cast<FunctionNoProtoType>(fnType))) {
    required = RequiredArgs(args.size());
  }

  // FIXME: Kill copy.
  SmallVector<CanQualType, 16> argTypes;
  for (const auto &arg : args)
    argTypes.push_back(CGT.getContext().getCanonicalParamType(arg.Ty));
  return CGT.arrangeLLVMFunctionInfo(GetReturnType(fnType->getReturnType()),
                                     /*instanceMethod=*/false, chainCall,
                                     argTypes, fnType->getExtInfo(), paramInfos,
                                     required);
}

/// Figure out the rules for calling a function with the given formal
/// type using the given arguments.  The arguments are necessary
/// because the function might be unprototyped, in which case it's
/// target-dependent in crazy ways.
const CGFunctionInfo &
CodeGenTypes::arrangeFreeFunctionCall(const CallArgList &args,
                                      const FunctionType *fnType,
                                      bool chainCall) {
  return arrangeFreeFunctionLikeCall(*this, CGM, args, fnType,
                                     chainCall ? 1 : 0, chainCall);
}

/// A block function is essentially a free function with an
/// extra implicit argument.
const CGFunctionInfo &
CodeGenTypes::arrangeBlockFunctionCall(const CallArgList &args,
                                       const FunctionType *fnType) {
  return arrangeFreeFunctionLikeCall(*this, CGM, args, fnType, 1,
                                     /*chainCall=*/false);
}

const CGFunctionInfo &
CodeGenTypes::arrangeBlockFunctionDeclaration(const FunctionProtoType *proto,
                                              const FunctionArgList &params) {
  auto paramInfos = getExtParameterInfosForCall(proto, 1, params.size());
  auto argTypes = getArgTypesForDeclaration(Context, params);

  return arrangeLLVMFunctionInfo(GetReturnType(proto->getReturnType()),
                                 /*instanceMethod*/ false, /*chainCall*/ false,
                                 argTypes, proto->getExtInfo(), paramInfos,
                                 RequiredArgs::forPrototypePlus(proto, 1));
}

const CGFunctionInfo &
CodeGenTypes::arrangeBuiltinFunctionCall(QualType resultType,
                                         const CallArgList &args) {
  // FIXME: Kill copy.
  SmallVector<CanQualType, 16> argTypes;
  for (const auto &Arg : args)
    argTypes.push_back(Context.getCanonicalParamType(Arg.Ty));
  return arrangeLLVMFunctionInfo(
      GetReturnType(resultType), /*instanceMethod=*/false,
      /*chainCall=*/false, argTypes, FunctionType::ExtInfo(),
      /*paramInfos=*/ {}, RequiredArgs::All);
}

const CGFunctionInfo &
CodeGenTypes::arrangeBuiltinFunctionDeclaration(QualType resultType,
                                                const FunctionArgList &args) {
  auto argTypes = getArgTypesForDeclaration(Context, args);

  return arrangeLLVMFunctionInfo(
      GetReturnType(resultType), /*instanceMethod=*/false, /*chainCall=*/false,
      argTypes, FunctionType::ExtInfo(), {}, RequiredArgs::All);
}

const CGFunctionInfo &
CodeGenTypes::arrangeBuiltinFunctionDeclaration(CanQualType resultType,
                                              ArrayRef<CanQualType> argTypes) {
  return arrangeLLVMFunctionInfo(
      resultType, /*instanceMethod=*/false, /*chainCall=*/false,
      argTypes, FunctionType::ExtInfo(), {}, RequiredArgs::All);
}

/// Arrange a call to a C++ method, passing the given arguments.
///
/// numPrefixArgs is the number of ABI-specific prefix arguments we have. It
/// does not count `this`.
const CGFunctionInfo &
CodeGenTypes::arrangeCXXMethodCall(const CallArgList &args,
                                   const FunctionProtoType *proto,
                                   RequiredArgs required,
                                   unsigned numPrefixArgs) {
  assert(numPrefixArgs + 1 <= args.size() &&
         "Emitting a call with less args than the required prefix?");
  // Add one to account for `this`. It's a bit awkward here, but we don't count
  // `this` in similar places elsewhere.
  auto paramInfos =
    getExtParameterInfosForCall(proto, numPrefixArgs + 1, args.size());

  // FIXME: Kill copy.
  auto argTypes = getArgTypesForCall(Context, args);

  FunctionType::ExtInfo info = proto->getExtInfo();
  return arrangeLLVMFunctionInfo(
      GetReturnType(proto->getReturnType()), /*instanceMethod=*/true,
      /*chainCall=*/false, argTypes, info, paramInfos, required);
}

const CGFunctionInfo &CodeGenTypes::arrangeNullaryFunction() {
  return arrangeLLVMFunctionInfo(
      getContext().VoidTy, /*instanceMethod=*/false, /*chainCall=*/false,
      None, FunctionType::ExtInfo(), {}, RequiredArgs::All);
}

const CGFunctionInfo &
CodeGenTypes::arrangeCall(const CGFunctionInfo &signature,
                          const CallArgList &args) {
  assert(signature.arg_size() <= args.size());
  if (signature.arg_size() == args.size())
    return signature;

  SmallVector<FunctionProtoType::ExtParameterInfo, 16> paramInfos;
  auto sigParamInfos = signature.getExtParameterInfos();
  if (!sigParamInfos.empty()) {
    paramInfos.append(sigParamInfos.begin(), sigParamInfos.end());
    paramInfos.resize(args.size());
  }

  auto argTypes = getArgTypesForCall(Context, args);

  assert(signature.getRequiredArgs().allowsOptionalArgs());
  return arrangeLLVMFunctionInfo(signature.getReturnType(),
                                 signature.isInstanceMethod(),
                                 signature.isChainCall(),
                                 argTypes,
                                 signature.getExtInfo(),
                                 paramInfos,
                                 signature.getRequiredArgs());
}

namespace clang {
namespace CodeGen {
void computeSPIRKernelABIInfo(CodeGenModule &CGM, CGFunctionInfo &FI);
}
}

/// Arrange the argument and result information for an abstract value
/// of a given function type.  This is the method which all of the
/// above functions ultimately defer to.
const CGFunctionInfo &
CodeGenTypes::arrangeLLVMFunctionInfo(CanQualType resultType,
                                      bool instanceMethod,
                                      bool chainCall,
                                      ArrayRef<CanQualType> argTypes,
                                      FunctionType::ExtInfo info,
                     ArrayRef<FunctionProtoType::ExtParameterInfo> paramInfos,
                                      RequiredArgs required) {
  assert(llvm::all_of(argTypes,
                      [](CanQualType T) { return T.isCanonicalAsParam(); }));

  // Lookup or create unique function info.
  llvm::FoldingSetNodeID ID;
  CGFunctionInfo::Profile(ID, instanceMethod, chainCall, info, paramInfos,
                          required, resultType, argTypes);

  void *insertPos = nullptr;
  CGFunctionInfo *FI = FunctionInfos.FindNodeOrInsertPos(ID, insertPos);
  if (FI)
    return *FI;

  unsigned CC = ClangCallConvToLLVMCallConv(info.getCC());

  // Construct the function info.  We co-allocate the ArgInfos.
  FI = CGFunctionInfo::create(CC, instanceMethod, chainCall, info,
                              paramInfos, resultType, argTypes, required);
  FunctionInfos.InsertNode(FI, insertPos);

  bool inserted = FunctionsBeingProcessed.insert(FI).second;
  (void)inserted;
  assert(inserted && "Recursively being processed?");

  // Compute ABI information.
  if (CC == llvm::CallingConv::SPIR_KERNEL) {
    // Force target independent argument handling for the host visible
    // kernel functions.
    computeSPIRKernelABIInfo(CGM, *FI);
  } else if (info.getCC() == CC_Swift) {
    swiftcall::computeABIInfo(CGM, *FI);
  } else {
    getABIInfo().computeInfo(*FI);
  }

  // Loop over all of the computed argument and return value info.  If any of
  // them are direct or extend without a specified coerce type, specify the
  // default now.
  ABIArgInfo &retInfo = FI->getReturnInfo();
  if (retInfo.canHaveCoerceToType() && retInfo.getCoerceToType() == nullptr)
    retInfo.setCoerceToType(ConvertType(FI->getReturnType()));

  for (auto &I : FI->arguments())
    if (I.info.canHaveCoerceToType() && I.info.getCoerceToType() == nullptr)
      I.info.setCoerceToType(ConvertType(I.type));

  bool erased = FunctionsBeingProcessed.erase(FI); (void)erased;
  assert(erased && "Not in set?");

  return *FI;
}

CGFunctionInfo *CGFunctionInfo::create(unsigned llvmCC,
                                       bool instanceMethod,
                                       bool chainCall,
                                       const FunctionType::ExtInfo &info,
                                       ArrayRef<ExtParameterInfo> paramInfos,
                                       CanQualType resultType,
                                       ArrayRef<CanQualType> argTypes,
                                       RequiredArgs required) {
  assert(paramInfos.empty() || paramInfos.size() == argTypes.size());
  assert(!required.allowsOptionalArgs() ||
         required.getNumRequiredArgs() <= argTypes.size());

  void *buffer =
    operator new(totalSizeToAlloc<ArgInfo,             ExtParameterInfo>(
                                  argTypes.size() + 1, paramInfos.size()));

  CGFunctionInfo *FI = new(buffer) CGFunctionInfo();
  FI->CallingConvention = llvmCC;
  FI->EffectiveCallingConvention = llvmCC;
  FI->ASTCallingConvention = info.getCC();
  FI->InstanceMethod = instanceMethod;
  FI->ChainCall = chainCall;
  FI->CmseNSCall = info.getCmseNSCall();
  FI->NoReturn = info.getNoReturn();
  FI->ReturnsRetained = info.getProducesResult();
  FI->NoCallerSavedRegs = info.getNoCallerSavedRegs();
  FI->NoCfCheck = info.getNoCfCheck();
  FI->Required = required;
  FI->HasRegParm = info.getHasRegParm();
  FI->RegParm = info.getRegParm();
  FI->ArgStruct = nullptr;
  FI->ArgStructAlign = 0;
  FI->NumArgs = argTypes.size();
  FI->HasExtParameterInfos = !paramInfos.empty();
  FI->getArgsBuffer()[0].type = resultType;
  for (unsigned i = 0, e = argTypes.size(); i != e; ++i)
    FI->getArgsBuffer()[i + 1].type = argTypes[i];
  for (unsigned i = 0, e = paramInfos.size(); i != e; ++i)
    FI->getExtParameterInfosBuffer()[i] = paramInfos[i];
  return FI;
}

/***/

namespace {
// ABIArgInfo::Expand implementation.

// Specifies the way QualType passed as ABIArgInfo::Expand is expanded.
struct TypeExpansion {
  enum TypeExpansionKind {
    // Elements of constant arrays are expanded recursively.
    TEK_ConstantArray,
    // Record fields are expanded recursively (but if record is a union, only
    // the field with the largest size is expanded).
    TEK_Record,
    // For complex types, real and imaginary parts are expanded recursively.
    TEK_Complex,
    // All other types are not expandable.
    TEK_None
  };

  const TypeExpansionKind Kind;

  TypeExpansion(TypeExpansionKind K) : Kind(K) {}
  virtual ~TypeExpansion() {}
};

struct ConstantArrayExpansion : TypeExpansion {
  QualType EltTy;
  uint64_t NumElts;

  ConstantArrayExpansion(QualType EltTy, uint64_t NumElts)
      : TypeExpansion(TEK_ConstantArray), EltTy(EltTy), NumElts(NumElts) {}
  static bool classof(const TypeExpansion *TE) {
    return TE->Kind == TEK_ConstantArray;
  }
};

struct RecordExpansion : TypeExpansion {
  SmallVector<const CXXBaseSpecifier *, 1> Bases;

  SmallVector<const FieldDecl *, 1> Fields;

  RecordExpansion(SmallVector<const CXXBaseSpecifier *, 1> &&Bases,
                  SmallVector<const FieldDecl *, 1> &&Fields)
      : TypeExpansion(TEK_Record), Bases(std::move(Bases)),
        Fields(std::move(Fields)) {}
  static bool classof(const TypeExpansion *TE) {
    return TE->Kind == TEK_Record;
  }
};

struct ComplexExpansion : TypeExpansion {
  QualType EltTy;

  ComplexExpansion(QualType EltTy) : TypeExpansion(TEK_Complex), EltTy(EltTy) {}
  static bool classof(const TypeExpansion *TE) {
    return TE->Kind == TEK_Complex;
  }
};

struct NoExpansion : TypeExpansion {
  NoExpansion() : TypeExpansion(TEK_None) {}
  static bool classof(const TypeExpansion *TE) {
    return TE->Kind == TEK_None;
  }
};
}  // namespace

static std::unique_ptr<TypeExpansion>
getTypeExpansion(QualType Ty, const ASTContext &Context) {
  if (const ConstantArrayType *AT = Context.getAsConstantArrayType(Ty)) {
    return std::make_unique<ConstantArrayExpansion>(
        AT->getElementType(), AT->getSize().getZExtValue());
  }
  if (const RecordType *RT = Ty->getAs<RecordType>()) {
    SmallVector<const CXXBaseSpecifier *, 1> Bases;
    SmallVector<const FieldDecl *, 1> Fields;
    const RecordDecl *RD = RT->getDecl();
    assert(!RD->hasFlexibleArrayMember() &&
           "Cannot expand structure with flexible array.");
    if (RD->isUnion()) {
      // Unions can be here only in degenerative cases - all the fields are same
      // after flattening. Thus we have to use the "largest" field.
      const FieldDecl *LargestFD = nullptr;
      CharUnits UnionSize = CharUnits::Zero();

      for (const auto *FD : RD->fields()) {
        if (FD->isZeroLengthBitField(Context))
          continue;
        assert(!FD->isBitField() &&
               "Cannot expand structure with bit-field members.");
        CharUnits FieldSize = Context.getTypeSizeInChars(FD->getType());
        if (UnionSize < FieldSize) {
          UnionSize = FieldSize;
          LargestFD = FD;
        }
      }
      if (LargestFD)
        Fields.push_back(LargestFD);
    } else {
      if (const auto *CXXRD = dyn_cast<CXXRecordDecl>(RD)) {
        assert(!CXXRD->isDynamicClass() &&
               "cannot expand vtable pointers in dynamic classes");
        for (const CXXBaseSpecifier &BS : CXXRD->bases())
          Bases.push_back(&BS);
      }

      for (const auto *FD : RD->fields()) {
        if (FD->isZeroLengthBitField(Context))
          continue;
        assert(!FD->isBitField() &&
               "Cannot expand structure with bit-field members.");
        Fields.push_back(FD);
      }
    }
    return std::make_unique<RecordExpansion>(std::move(Bases),
                                              std::move(Fields));
  }
  if (const ComplexType *CT = Ty->getAs<ComplexType>()) {
    return std::make_unique<ComplexExpansion>(CT->getElementType());
  }
  return std::make_unique<NoExpansion>();
}

static int getExpansionSize(QualType Ty, const ASTContext &Context) {
  auto Exp = getTypeExpansion(Ty, Context);
  if (auto CAExp = dyn_cast<ConstantArrayExpansion>(Exp.get())) {
    return CAExp->NumElts * getExpansionSize(CAExp->EltTy, Context);
  }
  if (auto RExp = dyn_cast<RecordExpansion>(Exp.get())) {
    int Res = 0;
    for (auto BS : RExp->Bases)
      Res += getExpansionSize(BS->getType(), Context);
    for (auto FD : RExp->Fields)
      Res += getExpansionSize(FD->getType(), Context);
    return Res;
  }
  if (isa<ComplexExpansion>(Exp.get()))
    return 2;
  assert(isa<NoExpansion>(Exp.get()));
  return 1;
}

void
CodeGenTypes::getExpandedTypes(QualType Ty,
                               SmallVectorImpl<llvm::Type *>::iterator &TI) {
  auto Exp = getTypeExpansion(Ty, Context);
  if (auto CAExp = dyn_cast<ConstantArrayExpansion>(Exp.get())) {
    for (int i = 0, n = CAExp->NumElts; i < n; i++) {
      getExpandedTypes(CAExp->EltTy, TI);
    }
  } else if (auto RExp = dyn_cast<RecordExpansion>(Exp.get())) {
    for (auto BS : RExp->Bases)
      getExpandedTypes(BS->getType(), TI);
    for (auto FD : RExp->Fields)
      getExpandedTypes(FD->getType(), TI);
  } else if (auto CExp = dyn_cast<ComplexExpansion>(Exp.get())) {
    llvm::Type *EltTy = ConvertType(CExp->EltTy);
    *TI++ = EltTy;
    *TI++ = EltTy;
  } else {
    assert(isa<NoExpansion>(Exp.get()));
    *TI++ = ConvertType(Ty);
  }
}

static void forConstantArrayExpansion(CodeGenFunction &CGF,
                                      ConstantArrayExpansion *CAE,
                                      Address BaseAddr,
                                      llvm::function_ref<void(Address)> Fn) {
  CharUnits EltSize = CGF.getContext().getTypeSizeInChars(CAE->EltTy);
  CharUnits EltAlign =
    BaseAddr.getAlignment().alignmentOfArrayElement(EltSize);

  for (int i = 0, n = CAE->NumElts; i < n; i++) {
    llvm::Value *EltAddr =
      CGF.Builder.CreateConstGEP2_32(nullptr, BaseAddr.getPointer(), 0, i);
    Fn(Address(EltAddr, EltAlign));
  }
}

void CodeGenFunction::ExpandTypeFromArgs(QualType Ty, LValue LV,
                                         llvm::Function::arg_iterator &AI) {
  assert(LV.isSimple() &&
         "Unexpected non-simple lvalue during struct expansion.");

  auto Exp = getTypeExpansion(Ty, getContext());
  if (auto CAExp = dyn_cast<ConstantArrayExpansion>(Exp.get())) {
    forConstantArrayExpansion(
        *this, CAExp, LV.getAddress(*this), [&](Address EltAddr) {
          LValue LV = MakeAddrLValue(EltAddr, CAExp->EltTy);
          ExpandTypeFromArgs(CAExp->EltTy, LV, AI);
        });
  } else if (auto RExp = dyn_cast<RecordExpansion>(Exp.get())) {
    Address This = LV.getAddress(*this);
    for (const CXXBaseSpecifier *BS : RExp->Bases) {
      // Perform a single step derived-to-base conversion.
      Address Base =
          GetAddressOfBaseClass(This, Ty->getAsCXXRecordDecl(), &BS, &BS + 1,
                                /*NullCheckValue=*/false, SourceLocation());
      LValue SubLV = MakeAddrLValue(Base, BS->getType());

      // Recurse onto bases.
      ExpandTypeFromArgs(BS->getType(), SubLV, AI);
    }
    for (auto FD : RExp->Fields) {
      // FIXME: What are the right qualifiers here?
      LValue SubLV = EmitLValueForFieldInitialization(LV, FD);
      ExpandTypeFromArgs(FD->getType(), SubLV, AI);
    }
  } else if (isa<ComplexExpansion>(Exp.get())) {
    auto realValue = &*AI++;
    auto imagValue = &*AI++;
    EmitStoreOfComplex(ComplexPairTy(realValue, imagValue), LV, /*init*/ true);
  } else {
    // Call EmitStoreOfScalar except when the lvalue is a bitfield to emit a
    // primitive store.
    assert(isa<NoExpansion>(Exp.get()));
    if (LV.isBitField())
      EmitStoreThroughLValue(RValue::get(&*AI++), LV);
    else
      EmitStoreOfScalar(&*AI++, LV);
  }
}

void CodeGenFunction::ExpandTypeToArgs(
    QualType Ty, CallArg Arg, llvm::FunctionType *IRFuncTy,
    SmallVectorImpl<llvm::Value *> &IRCallArgs, unsigned &IRCallArgPos) {
  auto Exp = getTypeExpansion(Ty, getContext());
  if (auto CAExp = dyn_cast<ConstantArrayExpansion>(Exp.get())) {
    Address Addr = Arg.hasLValue() ? Arg.getKnownLValue().getAddress(*this)
                                   : Arg.getKnownRValue().getAggregateAddress();
    forConstantArrayExpansion(
        *this, CAExp, Addr, [&](Address EltAddr) {
          CallArg EltArg = CallArg(
              convertTempToRValue(EltAddr, CAExp->EltTy, SourceLocation()),
              CAExp->EltTy);
          ExpandTypeToArgs(CAExp->EltTy, EltArg, IRFuncTy, IRCallArgs,
                           IRCallArgPos);
        });
  } else if (auto RExp = dyn_cast<RecordExpansion>(Exp.get())) {
    Address This = Arg.hasLValue() ? Arg.getKnownLValue().getAddress(*this)
                                   : Arg.getKnownRValue().getAggregateAddress();
    for (const CXXBaseSpecifier *BS : RExp->Bases) {
      // Perform a single step derived-to-base conversion.
      Address Base =
          GetAddressOfBaseClass(This, Ty->getAsCXXRecordDecl(), &BS, &BS + 1,
                                /*NullCheckValue=*/false, SourceLocation());
      CallArg BaseArg = CallArg(RValue::getAggregate(Base), BS->getType());

      // Recurse onto bases.
      ExpandTypeToArgs(BS->getType(), BaseArg, IRFuncTy, IRCallArgs,
                       IRCallArgPos);
    }

    LValue LV = MakeAddrLValue(This, Ty);
    for (auto FD : RExp->Fields) {
      CallArg FldArg =
          CallArg(EmitRValueForField(LV, FD, SourceLocation()), FD->getType());
      ExpandTypeToArgs(FD->getType(), FldArg, IRFuncTy, IRCallArgs,
                       IRCallArgPos);
    }
  } else if (isa<ComplexExpansion>(Exp.get())) {
    ComplexPairTy CV = Arg.getKnownRValue().getComplexVal();
    IRCallArgs[IRCallArgPos++] = CV.first;
    IRCallArgs[IRCallArgPos++] = CV.second;
  } else {
    assert(isa<NoExpansion>(Exp.get()));
    auto RV = Arg.getKnownRValue();
    assert(RV.isScalar() &&
           "Unexpected non-scalar rvalue during struct expansion.");

    // Insert a bitcast as needed.
    llvm::Value *V = RV.getScalarVal();
    if (IRCallArgPos < IRFuncTy->getNumParams() &&
        V->getType() != IRFuncTy->getParamType(IRCallArgPos))
      V = Builder.CreateBitCast(V, IRFuncTy->getParamType(IRCallArgPos));

    IRCallArgs[IRCallArgPos++] = V;
  }
}

/// Create a temporary allocation for the purposes of coercion.
static Address CreateTempAllocaForCoercion(CodeGenFunction &CGF, llvm::Type *Ty,
                                           CharUnits MinAlign,
                                           const Twine &Name = "tmp") {
  // Don't use an alignment that's worse than what LLVM would prefer.
  auto PrefAlign = CGF.CGM.getDataLayout().getPrefTypeAlignment(Ty);
  CharUnits Align = std::max(MinAlign, CharUnits::fromQuantity(PrefAlign));

  return CGF.CreateTempAlloca(Ty, Align, Name + ".coerce");
}

/// EnterStructPointerForCoercedAccess - Given a struct pointer that we are
/// accessing some number of bytes out of it, try to gep into the struct to get
/// at its inner goodness.  Dive as deep as possible without entering an element
/// with an in-memory size smaller than DstSize.
static Address
EnterStructPointerForCoercedAccess(Address SrcPtr,
                                   llvm::StructType *SrcSTy,
                                   uint64_t DstSize, CodeGenFunction &CGF) {
  // We can't dive into a zero-element struct.
  if (SrcSTy->getNumElements() == 0) return SrcPtr;

  llvm::Type *FirstElt = SrcSTy->getElementType(0);

  // If the first elt is at least as large as what we're looking for, or if the
  // first element is the same size as the whole struct, we can enter it. The
  // comparison must be made on the store size and not the alloca size. Using
  // the alloca size may overstate the size of the load.
  uint64_t FirstEltSize =
    CGF.CGM.getDataLayout().getTypeStoreSize(FirstElt);
  if (FirstEltSize < DstSize &&
      FirstEltSize < CGF.CGM.getDataLayout().getTypeStoreSize(SrcSTy))
    return SrcPtr;

  // GEP into the first element.
  SrcPtr = CGF.Builder.CreateStructGEP(SrcPtr, 0, "coerce.dive");

  // If the first element is a struct, recurse.
  llvm::Type *SrcTy = SrcPtr.getElementType();
  if (llvm::StructType *SrcSTy = dyn_cast<llvm::StructType>(SrcTy))
    return EnterStructPointerForCoercedAccess(SrcPtr, SrcSTy, DstSize, CGF);

  return SrcPtr;
}

/// CoerceIntOrPtrToIntOrPtr - Convert a value Val to the specific Ty where both
/// are either integers or pointers.  This does a truncation of the value if it
/// is too large or a zero extension if it is too small.
///
/// This behaves as if the value were coerced through memory, so on big-endian
/// targets the high bits are preserved in a truncation, while little-endian
/// targets preserve the low bits.
static llvm::Value *CoerceIntOrPtrToIntOrPtr(llvm::Value *Val,
                                             llvm::Type *Ty,
                                             CodeGenFunction &CGF) {
  if (Val->getType() == Ty)
    return Val;

  if (isa<llvm::PointerType>(Val->getType())) {
    // If this is Pointer->Pointer avoid conversion to and from int.
    if (isa<llvm::PointerType>(Ty))
      return CGF.Builder.CreateBitCast(Val, Ty, "coerce.val");

    // Convert the pointer to an integer so we can play with its width.
    Val = CGF.Builder.CreatePtrToInt(Val, CGF.IntPtrTy, "coerce.val.pi");
  }

  llvm::Type *DestIntTy = Ty;
  if (isa<llvm::PointerType>(DestIntTy))
    DestIntTy = CGF.IntPtrTy;

  if (Val->getType() != DestIntTy) {
    const llvm::DataLayout &DL = CGF.CGM.getDataLayout();
    if (DL.isBigEndian()) {
      // Preserve the high bits on big-endian targets.
      // That is what memory coercion does.
      uint64_t SrcSize = DL.getTypeSizeInBits(Val->getType());
      uint64_t DstSize = DL.getTypeSizeInBits(DestIntTy);

      if (SrcSize > DstSize) {
        Val = CGF.Builder.CreateLShr(Val, SrcSize - DstSize, "coerce.highbits");
        Val = CGF.Builder.CreateTrunc(Val, DestIntTy, "coerce.val.ii");
      } else {
        Val = CGF.Builder.CreateZExt(Val, DestIntTy, "coerce.val.ii");
        Val = CGF.Builder.CreateShl(Val, DstSize - SrcSize, "coerce.highbits");
      }
    } else {
      // Little-endian targets preserve the low bits. No shifts required.
      Val = CGF.Builder.CreateIntCast(Val, DestIntTy, false, "coerce.val.ii");
    }
  }

  if (isa<llvm::PointerType>(Ty))
    Val = CGF.Builder.CreateIntToPtr(Val, Ty, "coerce.val.ip");
  return Val;
}



/// CreateCoercedLoad - Create a load from \arg SrcPtr interpreted as
/// a pointer to an object of type \arg Ty, known to be aligned to
/// \arg SrcAlign bytes.
///
/// This safely handles the case when the src type is smaller than the
/// destination type; in this situation the values of bits which not
/// present in the src are undefined.
static llvm::Value *CreateCoercedLoad(Address Src, llvm::Type *Ty,
                                      CodeGenFunction &CGF) {
  llvm::Type *SrcTy = Src.getElementType();

  // If SrcTy and Ty are the same, just do a load.
  if (SrcTy == Ty)
    return CGF.Builder.CreateLoad(Src);

  llvm::TypeSize DstSize = CGF.CGM.getDataLayout().getTypeAllocSize(Ty);

  if (llvm::StructType *SrcSTy = dyn_cast<llvm::StructType>(SrcTy)) {
    Src = EnterStructPointerForCoercedAccess(Src, SrcSTy,
                                             DstSize.getFixedSize(), CGF);
    SrcTy = Src.getElementType();
  }

  llvm::TypeSize SrcSize = CGF.CGM.getDataLayout().getTypeAllocSize(SrcTy);

  // If the source and destination are integer or pointer types, just do an
  // extension or truncation to the desired type.
  if ((isa<llvm::IntegerType>(Ty) || isa<llvm::PointerType>(Ty)) &&
      (isa<llvm::IntegerType>(SrcTy) || isa<llvm::PointerType>(SrcTy))) {
    llvm::Value *Load = CGF.Builder.CreateLoad(Src);
    return CoerceIntOrPtrToIntOrPtr(Load, Ty, CGF);
  }

  // If load is legal, just bitcast the src pointer.
  if (!SrcSize.isScalable() && !DstSize.isScalable() &&
      SrcSize.getFixedSize() >= DstSize.getFixedSize()) {
    // Generally SrcSize is never greater than DstSize, since this means we are
    // losing bits. However, this can happen in cases where the structure has
    // additional padding, for example due to a user specified alignment.
    //
    // FIXME: Assert that we aren't truncating non-padding bits when have access
    // to that information.
    Src = CGF.Builder.CreateBitCast(Src,
                                    Ty->getPointerTo(Src.getAddressSpace()));
    return CGF.Builder.CreateLoad(Src);
  }

  // Otherwise do coercion through memory. This is stupid, but simple.
  Address Tmp =
      CreateTempAllocaForCoercion(CGF, Ty, Src.getAlignment(), Src.getName());
  CGF.Builder.CreateMemCpy(
      Tmp.getPointer(), Tmp.getAlignment().getAsAlign(), Src.getPointer(),
      Src.getAlignment().getAsAlign(),
      llvm::ConstantInt::get(CGF.IntPtrTy, SrcSize.getKnownMinSize()));
  return CGF.Builder.CreateLoad(Tmp);
}

// Function to store a first-class aggregate into memory.  We prefer to
// store the elements rather than the aggregate to be more friendly to
// fast-isel.
// FIXME: Do we need to recurse here?
void CodeGenFunction::EmitAggregateStore(llvm::Value *Val, Address Dest,
                                         bool DestIsVolatile) {
  // Prefer scalar stores to first-class aggregate stores.
  if (llvm::StructType *STy = dyn_cast<llvm::StructType>(Val->getType())) {
    for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
      Address EltPtr = Builder.CreateStructGEP(Dest, i);
      llvm::Value *Elt = Builder.CreateExtractValue(Val, i);
      Builder.CreateStore(Elt, EltPtr, DestIsVolatile);
    }
  } else {
    Builder.CreateStore(Val, Dest, DestIsVolatile);
  }
}

/// CreateCoercedStore - Create a store to \arg DstPtr from \arg Src,
/// where the source and destination may have different types.  The
/// destination is known to be aligned to \arg DstAlign bytes.
///
/// This safely handles the case when the src type is larger than the
/// destination type; the upper bits of the src will be lost.
static void CreateCoercedStore(llvm::Value *Src,
                               Address Dst,
                               bool DstIsVolatile,
                               CodeGenFunction &CGF) {
  llvm::Type *SrcTy = Src->getType();
  llvm::Type *DstTy = Dst.getElementType();
  if (SrcTy == DstTy) {
    CGF.Builder.CreateStore(Src, Dst, DstIsVolatile);
    return;
  }

  llvm::TypeSize SrcSize = CGF.CGM.getDataLayout().getTypeAllocSize(SrcTy);

  if (llvm::StructType *DstSTy = dyn_cast<llvm::StructType>(DstTy)) {
    Dst = EnterStructPointerForCoercedAccess(Dst, DstSTy,
                                             SrcSize.getFixedSize(), CGF);
    DstTy = Dst.getElementType();
  }

  llvm::PointerType *SrcPtrTy = llvm::dyn_cast<llvm::PointerType>(SrcTy);
  llvm::PointerType *DstPtrTy = llvm::dyn_cast<llvm::PointerType>(DstTy);
  if (SrcPtrTy && DstPtrTy &&
      SrcPtrTy->getAddressSpace() != DstPtrTy->getAddressSpace()) {
    Src = CGF.Builder.CreatePointerBitCastOrAddrSpaceCast(Src, DstTy);
    CGF.Builder.CreateStore(Src, Dst, DstIsVolatile);
    return;
  }

  // If the source and destination are integer or pointer types, just do an
  // extension or truncation to the desired type.
  if ((isa<llvm::IntegerType>(SrcTy) || isa<llvm::PointerType>(SrcTy)) &&
      (isa<llvm::IntegerType>(DstTy) || isa<llvm::PointerType>(DstTy))) {
    Src = CoerceIntOrPtrToIntOrPtr(Src, DstTy, CGF);
    CGF.Builder.CreateStore(Src, Dst, DstIsVolatile);
    return;
  }

  llvm::TypeSize DstSize = CGF.CGM.getDataLayout().getTypeAllocSize(DstTy);

  // If store is legal, just bitcast the src pointer.
  if (isa<llvm::ScalableVectorType>(SrcTy) ||
      isa<llvm::ScalableVectorType>(DstTy) ||
      SrcSize.getFixedSize() <= DstSize.getFixedSize()) {
    Dst = CGF.Builder.CreateElementBitCast(Dst, SrcTy);
    CGF.EmitAggregateStore(Src, Dst, DstIsVolatile);
  } else {
    // Otherwise do coercion through memory. This is stupid, but
    // simple.

    // Generally SrcSize is never greater than DstSize, since this means we are
    // losing bits. However, this can happen in cases where the structure has
    // additional padding, for example due to a user specified alignment.
    //
    // FIXME: Assert that we aren't truncating non-padding bits when have access
    // to that information.
    Address Tmp = CreateTempAllocaForCoercion(CGF, SrcTy, Dst.getAlignment());
    CGF.Builder.CreateStore(Src, Tmp);
    CGF.Builder.CreateMemCpy(
        Dst.getPointer(), Dst.getAlignment().getAsAlign(), Tmp.getPointer(),
        Tmp.getAlignment().getAsAlign(),
        llvm::ConstantInt::get(CGF.IntPtrTy, DstSize.getFixedSize()));
  }
}

static Address emitAddressAtOffset(CodeGenFunction &CGF, Address addr,
                                   const ABIArgInfo &info) {
  if (unsigned offset = info.getDirectOffset()) {
    addr = CGF.Builder.CreateElementBitCast(addr, CGF.Int8Ty);
    addr = CGF.Builder.CreateConstInBoundsByteGEP(addr,
                                             CharUnits::fromQuantity(offset));
    addr = CGF.Builder.CreateElementBitCast(addr, info.getCoerceToType());
  }
  return addr;
}

namespace {

/// Encapsulates information about the way function arguments from
/// CGFunctionInfo should be passed to actual LLVM IR function.
class ClangToLLVMArgMapping {
  static const unsigned InvalidIndex = ~0U;
  unsigned InallocaArgNo;
  unsigned SRetArgNo;
  unsigned TotalIRArgs;

  /// Arguments of LLVM IR function corresponding to single Clang argument.
  struct IRArgs {
    unsigned PaddingArgIndex;
    // Argument is expanded to IR arguments at positions
    // [FirstArgIndex, FirstArgIndex + NumberOfArgs).
    unsigned FirstArgIndex;
    unsigned NumberOfArgs;

    IRArgs()
        : PaddingArgIndex(InvalidIndex), FirstArgIndex(InvalidIndex),
          NumberOfArgs(0) {}
  };

  SmallVector<IRArgs, 8> ArgInfo;

public:
  ClangToLLVMArgMapping(const ASTContext &Context, const CGFunctionInfo &FI,
                        bool OnlyRequiredArgs = false)
      : InallocaArgNo(InvalidIndex), SRetArgNo(InvalidIndex), TotalIRArgs(0),
        ArgInfo(OnlyRequiredArgs ? FI.getNumRequiredArgs() : FI.arg_size()) {
    construct(Context, FI, OnlyRequiredArgs);
  }

  bool hasInallocaArg() const { return InallocaArgNo != InvalidIndex; }
  unsigned getInallocaArgNo() const {
    assert(hasInallocaArg());
    return InallocaArgNo;
  }

  bool hasSRetArg() const { return SRetArgNo != InvalidIndex; }
  unsigned getSRetArgNo() const {
    assert(hasSRetArg());
    return SRetArgNo;
  }

  unsigned totalIRArgs() const { return TotalIRArgs; }

  bool hasPaddingArg(unsigned ArgNo) const {
    assert(ArgNo < ArgInfo.size());
    return ArgInfo[ArgNo].PaddingArgIndex != InvalidIndex;
  }
  unsigned getPaddingArgNo(unsigned ArgNo) const {
    assert(hasPaddingArg(ArgNo));
    return ArgInfo[ArgNo].PaddingArgIndex;
  }

  /// Returns index of first IR argument corresponding to ArgNo, and their
  /// quantity.
  std::pair<unsigned, unsigned> getIRArgs(unsigned ArgNo) const {
    assert(ArgNo < ArgInfo.size());
    return std::make_pair(ArgInfo[ArgNo].FirstArgIndex,
                          ArgInfo[ArgNo].NumberOfArgs);
  }

private:
  void construct(const ASTContext &Context, const CGFunctionInfo &FI,
                 bool OnlyRequiredArgs);
};

void ClangToLLVMArgMapping::construct(const ASTContext &Context,
                                      const CGFunctionInfo &FI,
                                      bool OnlyRequiredArgs) {
  unsigned IRArgNo = 0;
  bool SwapThisWithSRet = false;
  const ABIArgInfo &RetAI = FI.getReturnInfo();

  if (RetAI.getKind() == ABIArgInfo::Indirect) {
    SwapThisWithSRet = RetAI.isSRetAfterThis();
    SRetArgNo = SwapThisWithSRet ? 1 : IRArgNo++;
  }

  unsigned ArgNo = 0;
  unsigned NumArgs = OnlyRequiredArgs ? FI.getNumRequiredArgs() : FI.arg_size();
  for (CGFunctionInfo::const_arg_iterator I = FI.arg_begin(); ArgNo < NumArgs;
       ++I, ++ArgNo) {
    assert(I != FI.arg_end());
    QualType ArgType = I->type;
    const ABIArgInfo &AI = I->info;
    // Collect data about IR arguments corresponding to Clang argument ArgNo.
    auto &IRArgs = ArgInfo[ArgNo];

    if (AI.getPaddingType())
      IRArgs.PaddingArgIndex = IRArgNo++;

    switch (AI.getKind()) {
    case ABIArgInfo::Extend:
    case ABIArgInfo::Direct: {
      // FIXME: handle sseregparm someday...
      llvm::StructType *STy = dyn_cast<llvm::StructType>(AI.getCoerceToType());
      if (AI.isDirect() && AI.getCanBeFlattened() && STy) {
        IRArgs.NumberOfArgs = STy->getNumElements();
      } else {
        IRArgs.NumberOfArgs = 1;
      }
      break;
    }
    case ABIArgInfo::Indirect:
    case ABIArgInfo::IndirectAliased:
      IRArgs.NumberOfArgs = 1;
      break;
    case ABIArgInfo::Ignore:
    case ABIArgInfo::InAlloca:
      // ignore and inalloca doesn't have matching LLVM parameters.
      IRArgs.NumberOfArgs = 0;
      break;
    case ABIArgInfo::CoerceAndExpand:
      IRArgs.NumberOfArgs = AI.getCoerceAndExpandTypeSequence().size();
      break;
    case ABIArgInfo::Expand:
      IRArgs.NumberOfArgs = getExpansionSize(ArgType, Context);
      break;
    }

    if (IRArgs.NumberOfArgs > 0) {
      IRArgs.FirstArgIndex = IRArgNo;
      IRArgNo += IRArgs.NumberOfArgs;
    }

    // Skip over the sret parameter when it comes second.  We already handled it
    // above.
    if (IRArgNo == 1 && SwapThisWithSRet)
      IRArgNo++;
  }
  assert(ArgNo == ArgInfo.size());

  if (FI.usesInAlloca())
    InallocaArgNo = IRArgNo++;

  TotalIRArgs = IRArgNo;
}
}  // namespace

/***/

bool CodeGenModule::ReturnTypeUsesSRet(const CGFunctionInfo &FI) {
  const auto &RI = FI.getReturnInfo();
  return RI.isIndirect() || (RI.isInAlloca() && RI.getInAllocaSRet());
}

bool CodeGenModule::ReturnSlotInterferesWithArgs(const CGFunctionInfo &FI) {
  return ReturnTypeUsesSRet(FI) &&
         getTargetCodeGenInfo().doesReturnSlotInterfereWithArgs();
}

bool CodeGenModule::ReturnTypeUsesFPRet(QualType ResultType) {
  if (const BuiltinType *BT = ResultType->getAs<BuiltinType>()) {
    switch (BT->getKind()) {
    default:
      return false;
    case BuiltinType::Float:
      return getTarget().useObjCFPRetForRealType(TargetInfo::Float);
    case BuiltinType::Double:
      return getTarget().useObjCFPRetForRealType(TargetInfo::Double);
    case BuiltinType::LongDouble:
      return getTarget().useObjCFPRetForRealType(TargetInfo::LongDouble);
    }
  }

  return false;
}

bool CodeGenModule::ReturnTypeUsesFP2Ret(QualType ResultType) {
  if (const ComplexType *CT = ResultType->getAs<ComplexType>()) {
    if (const BuiltinType *BT = CT->getElementType()->getAs<BuiltinType>()) {
      if (BT->getKind() == BuiltinType::LongDouble)
        return getTarget().useObjCFP2RetForComplexLongDouble();
    }
  }

  return false;
}

llvm::FunctionType *CodeGenTypes::GetFunctionType(GlobalDecl GD) {
  const CGFunctionInfo &FI = arrangeGlobalDeclaration(GD);
  return GetFunctionType(FI);
}

llvm::FunctionType *
CodeGenTypes::GetFunctionType(const CGFunctionInfo &FI) {

  bool Inserted = FunctionsBeingProcessed.insert(&FI).second;
  (void)Inserted;
  assert(Inserted && "Recursively being processed?");

  llvm::Type *resultType = nullptr;
  const ABIArgInfo &retAI = FI.getReturnInfo();
  switch (retAI.getKind()) {
  case ABIArgInfo::Expand:
  case ABIArgInfo::IndirectAliased:
    llvm_unreachable("Invalid ABI kind for return argument");

  case ABIArgInfo::Extend:
  case ABIArgInfo::Direct:
    resultType = retAI.getCoerceToType();
    break;

  case ABIArgInfo::InAlloca:
    if (retAI.getInAllocaSRet()) {
      // sret things on win32 aren't void, they return the sret pointer.
      QualType ret = FI.getReturnType();
      llvm::Type *ty = ConvertType(ret);
      unsigned addressSpace = Context.getTargetAddressSpace(ret);
      resultType = llvm::PointerType::get(ty, addressSpace);
    } else {
      resultType = llvm::Type::getVoidTy(getLLVMContext());
    }
    break;

  case ABIArgInfo::Indirect:
  case ABIArgInfo::Ignore:
    resultType = llvm::Type::getVoidTy(getLLVMContext());
    break;

  case ABIArgInfo::CoerceAndExpand:
    resultType = retAI.getUnpaddedCoerceAndExpandType();
    break;
  }

  ClangToLLVMArgMapping IRFunctionArgs(getContext(), FI, true);
  SmallVector<llvm::Type*, 8> ArgTypes(IRFunctionArgs.totalIRArgs());

  // Add type for sret argument.
  if (IRFunctionArgs.hasSRetArg()) {
    QualType Ret = FI.getReturnType();
    llvm::Type *Ty = ConvertType(Ret);
    unsigned AddressSpace = Context.getTargetAddressSpace(Ret);
    ArgTypes[IRFunctionArgs.getSRetArgNo()] =
        llvm::PointerType::get(Ty, AddressSpace);
  }

  // Add type for inalloca argument.
  if (IRFunctionArgs.hasInallocaArg()) {
    auto ArgStruct = FI.getArgStruct();
    assert(ArgStruct);
    ArgTypes[IRFunctionArgs.getInallocaArgNo()] = ArgStruct->getPointerTo();
  }

  // Add in all of the required arguments.
  unsigned ArgNo = 0;
  CGFunctionInfo::const_arg_iterator it = FI.arg_begin(),
                                     ie = it + FI.getNumRequiredArgs();
  for (; it != ie; ++it, ++ArgNo) {
    const ABIArgInfo &ArgInfo = it->info;

    // Insert a padding type to ensure proper alignment.
    if (IRFunctionArgs.hasPaddingArg(ArgNo))
      ArgTypes[IRFunctionArgs.getPaddingArgNo(ArgNo)] =
          ArgInfo.getPaddingType();

    unsigned FirstIRArg, NumIRArgs;
    std::tie(FirstIRArg, NumIRArgs) = IRFunctionArgs.getIRArgs(ArgNo);

    switch (ArgInfo.getKind()) {
    case ABIArgInfo::Ignore:
    case ABIArgInfo::InAlloca:
      assert(NumIRArgs == 0);
      break;

    case ABIArgInfo::Indirect: {
      assert(NumIRArgs == 1);
      // indirect arguments are always on the stack, which is alloca addr space.
      llvm::Type *LTy = ConvertTypeForMem(it->type);
      ArgTypes[FirstIRArg] = LTy->getPointerTo(
          CGM.getDataLayout().getAllocaAddrSpace());
      break;
    }
    case ABIArgInfo::IndirectAliased: {
      assert(NumIRArgs == 1);
      llvm::Type *LTy = ConvertTypeForMem(it->type);
      ArgTypes[FirstIRArg] = LTy->getPointerTo(ArgInfo.getIndirectAddrSpace());
      break;
    }
    case ABIArgInfo::Extend:
    case ABIArgInfo::Direct: {
      // Fast-isel and the optimizer generally like scalar values better than
      // FCAs, so we flatten them if this is safe to do for this argument.
      llvm::Type *argType = ArgInfo.getCoerceToType();
      llvm::StructType *st = dyn_cast<llvm::StructType>(argType);
      if (st && ArgInfo.isDirect() && ArgInfo.getCanBeFlattened()) {
        assert(NumIRArgs == st->getNumElements());
        for (unsigned i = 0, e = st->getNumElements(); i != e; ++i)
          ArgTypes[FirstIRArg + i] = st->getElementType(i);
      } else {
        assert(NumIRArgs == 1);
        ArgTypes[FirstIRArg] = argType;
      }
      break;
    }

    case ABIArgInfo::CoerceAndExpand: {
      auto ArgTypesIter = ArgTypes.begin() + FirstIRArg;
      for (auto EltTy : ArgInfo.getCoerceAndExpandTypeSequence()) {
        *ArgTypesIter++ = EltTy;
      }
      assert(ArgTypesIter == ArgTypes.begin() + FirstIRArg + NumIRArgs);
      break;
    }

    case ABIArgInfo::Expand:
      auto ArgTypesIter = ArgTypes.begin() + FirstIRArg;
      getExpandedTypes(it->type, ArgTypesIter);
      assert(ArgTypesIter == ArgTypes.begin() + FirstIRArg + NumIRArgs);
      break;
    }
  }

  bool Erased = FunctionsBeingProcessed.erase(&FI); (void)Erased;
  assert(Erased && "Not in set?");

  return llvm::FunctionType::get(resultType, ArgTypes, FI.isVariadic());
}

llvm::Type *CodeGenTypes::GetFunctionTypeForVTable(GlobalDecl GD) {
  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();

  if (!isFuncTypeConvertible(FPT))
    return llvm::StructType::get(getLLVMContext());

  return GetFunctionType(GD);
}

static void AddAttributesFromFunctionProtoType(ASTContext &Ctx,
                                               llvm::AttrBuilder &FuncAttrs,
                                               const FunctionProtoType *FPT) {
  if (!FPT)
    return;

  if (!isUnresolvedExceptionSpec(FPT->getExceptionSpecType()) &&
      FPT->isNothrow())
    FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
}

void CodeGenModule::getDefaultFunctionAttributes(StringRef Name,
                                                 bool HasOptnone,
                                                 bool AttrOnCallSite,
                                               llvm::AttrBuilder &FuncAttrs) {
  // OptimizeNoneAttr takes precedence over -Os or -Oz. No warning needed.
  if (!HasOptnone) {
    if (CodeGenOpts.OptimizeSize)
      FuncAttrs.addAttribute(llvm::Attribute::OptimizeForSize);
    if (CodeGenOpts.OptimizeSize == 2)
      FuncAttrs.addAttribute(llvm::Attribute::MinSize);
  }

  if (CodeGenOpts.DisableRedZone)
    FuncAttrs.addAttribute(llvm::Attribute::NoRedZone);
  if (CodeGenOpts.IndirectTlsSegRefs)
    FuncAttrs.addAttribute("indirect-tls-seg-refs");
  if (CodeGenOpts.NoImplicitFloat)
    FuncAttrs.addAttribute(llvm::Attribute::NoImplicitFloat);

  if (AttrOnCallSite) {
    // Attributes that should go on the call site only.
    if (!CodeGenOpts.SimplifyLibCalls ||
        CodeGenOpts.isNoBuiltinFunc(Name.data()))
      FuncAttrs.addAttribute(llvm::Attribute::NoBuiltin);
    if (!CodeGenOpts.TrapFuncName.empty())
      FuncAttrs.addAttribute("trap-func-name", CodeGenOpts.TrapFuncName);
  } else {
    StringRef FpKind;
    switch (CodeGenOpts.getFramePointer()) {
    case CodeGenOptions::FramePointerKind::None:
      FpKind = "none";
      break;
    case CodeGenOptions::FramePointerKind::NonLeaf:
      FpKind = "non-leaf";
      break;
    case CodeGenOptions::FramePointerKind::All:
      FpKind = "all";
      break;
    }
    FuncAttrs.addAttribute("frame-pointer", FpKind);

    FuncAttrs.addAttribute("less-precise-fpmad",
                           llvm::toStringRef(CodeGenOpts.LessPreciseFPMAD));

    if (CodeGenOpts.NullPointerIsValid)
      FuncAttrs.addAttribute(llvm::Attribute::NullPointerIsValid);

    if (CodeGenOpts.FPDenormalMode != llvm::DenormalMode::getIEEE())
      FuncAttrs.addAttribute("denormal-fp-math",
                             CodeGenOpts.FPDenormalMode.str());
    if (CodeGenOpts.FP32DenormalMode != CodeGenOpts.FPDenormalMode) {
      FuncAttrs.addAttribute(
          "denormal-fp-math-f32",
          CodeGenOpts.FP32DenormalMode.str());
    }

    FuncAttrs.addAttribute("no-trapping-math",
                           llvm::toStringRef(LangOpts.getFPExceptionMode() ==
                                             LangOptions::FPE_Ignore));

    // Strict (compliant) code is the default, so only add this attribute to
    // indicate that we are trying to workaround a problem case.
    if (!CodeGenOpts.StrictFloatCastOverflow)
      FuncAttrs.addAttribute("strict-float-cast-overflow", "false");

    // TODO: Are these all needed?
    // unsafe/inf/nan/nsz are handled by instruction-level FastMathFlags.
    FuncAttrs.addAttribute("no-infs-fp-math",
                           llvm::toStringRef(LangOpts.NoHonorInfs));
    FuncAttrs.addAttribute("no-nans-fp-math",
                           llvm::toStringRef(LangOpts.NoHonorNaNs));
    FuncAttrs.addAttribute("unsafe-fp-math",
                           llvm::toStringRef(LangOpts.UnsafeFPMath));
    FuncAttrs.addAttribute("use-soft-float",
                           llvm::toStringRef(CodeGenOpts.SoftFloat));
    FuncAttrs.addAttribute("stack-protector-buffer-size",
                           llvm::utostr(CodeGenOpts.SSPBufferSize));
    FuncAttrs.addAttribute("no-signed-zeros-fp-math",
                           llvm::toStringRef(LangOpts.NoSignedZero));

    // TODO: Reciprocal estimate codegen options should apply to instructions?
    const std::vector<std::string> &Recips = CodeGenOpts.Reciprocals;
    if (!Recips.empty())
      FuncAttrs.addAttribute("reciprocal-estimates",
                             llvm::join(Recips, ","));

    if (!CodeGenOpts.PreferVectorWidth.empty() &&
        CodeGenOpts.PreferVectorWidth != "none")
      FuncAttrs.addAttribute("prefer-vector-width",
                             CodeGenOpts.PreferVectorWidth);

    if (CodeGenOpts.StackRealignment)
      FuncAttrs.addAttribute("stackrealign");
    if (CodeGenOpts.Backchain)
      FuncAttrs.addAttribute("backchain");
    if (CodeGenOpts.EnableSegmentedStacks)
      FuncAttrs.addAttribute("split-stack");

    if (CodeGenOpts.SpeculativeLoadHardening)
      FuncAttrs.addAttribute(llvm::Attribute::SpeculativeLoadHardening);
  }

  if (getLangOpts().assumeFunctionsAreConvergent()) {
    // Conservatively, mark all functions and calls in CUDA and OpenCL as
    // convergent (meaning, they may call an intrinsically convergent op, such
    // as __syncthreads() / barrier(), and so can't have certain optimizations
    // applied around them).  LLVM will remove this attribute where it safely
    // can.
    FuncAttrs.addAttribute(llvm::Attribute::Convergent);
  }

  if (getLangOpts().CUDA && getLangOpts().CUDAIsDevice) {
    // Exceptions aren't supported in CUDA device code.
    FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
  }

  for (StringRef Attr : CodeGenOpts.DefaultFunctionAttrs) {
    StringRef Var, Value;
    std::tie(Var, Value) = Attr.split('=');
    FuncAttrs.addAttribute(Var, Value);
  }
}

void CodeGenModule::addDefaultFunctionDefinitionAttributes(llvm::Function &F) {
  llvm::AttrBuilder FuncAttrs;
  getDefaultFunctionAttributes(F.getName(), F.hasOptNone(),
                               /* AttrOnCallSite = */ false, FuncAttrs);
  // TODO: call GetCPUAndFeaturesAttributes?
  F.addAttributes(llvm::AttributeList::FunctionIndex, FuncAttrs);
}

void CodeGenModule::addDefaultFunctionDefinitionAttributes(
                                                   llvm::AttrBuilder &attrs) {
  getDefaultFunctionAttributes(/*function name*/ "", /*optnone*/ false,
                               /*for call*/ false, attrs);
  GetCPUAndFeaturesAttributes(GlobalDecl(), attrs);
}

static void addNoBuiltinAttributes(llvm::AttrBuilder &FuncAttrs,
                                   const LangOptions &LangOpts,
                                   const NoBuiltinAttr *NBA = nullptr) {
  auto AddNoBuiltinAttr = [&FuncAttrs](StringRef BuiltinName) {
    SmallString<32> AttributeName;
    AttributeName += "no-builtin-";
    AttributeName += BuiltinName;
    FuncAttrs.addAttribute(AttributeName);
  };

  // First, handle the language options passed through -fno-builtin.
  if (LangOpts.NoBuiltin) {
    // -fno-builtin disables them all.
    FuncAttrs.addAttribute("no-builtins");
    return;
  }

  // Then, add attributes for builtins specified through -fno-builtin-<name>.
  llvm::for_each(LangOpts.NoBuiltinFuncs, AddNoBuiltinAttr);

  // Now, let's check the __attribute__((no_builtin("...")) attribute added to
  // the source.
  if (!NBA)
    return;

  // If there is a wildcard in the builtin names specified through the
  // attribute, disable them all.
  if (llvm::is_contained(NBA->builtinNames(), "*")) {
    FuncAttrs.addAttribute("no-builtins");
    return;
  }

  // And last, add the rest of the builtin names.
  llvm::for_each(NBA->builtinNames(), AddNoBuiltinAttr);
}

/// Construct the IR attribute list of a function or call.
///
/// When adding an attribute, please consider where it should be handled:
///
///   - getDefaultFunctionAttributes is for attributes that are essentially
///     part of the global target configuration (but perhaps can be
///     overridden on a per-function basis).  Adding attributes there
///     will cause them to also be set in frontends that build on Clang's
///     target-configuration logic, as well as for code defined in library
///     modules such as CUDA's libdevice.
///
///   - ConstructAttributeList builds on top of getDefaultFunctionAttributes
///     and adds declaration-specific, convention-specific, and
///     frontend-specific logic.  The last is of particular importance:
///     attributes that restrict how the frontend generates code must be
///     added here rather than getDefaultFunctionAttributes.
///
void CodeGenModule::ConstructAttributeList(
    StringRef Name, const CGFunctionInfo &FI, CGCalleeInfo CalleeInfo,
    llvm::AttributeList &AttrList, unsigned &CallingConv, bool AttrOnCallSite) {
  llvm::AttrBuilder FuncAttrs;
  llvm::AttrBuilder RetAttrs;

  // Collect function IR attributes from the CC lowering.
  // We'll collect the paramete and result attributes later.
  CallingConv = FI.getEffectiveCallingConvention();
  if (FI.isNoReturn())
    FuncAttrs.addAttribute(llvm::Attribute::NoReturn);
  if (FI.isCmseNSCall())
    FuncAttrs.addAttribute("cmse_nonsecure_call");

  // Collect function IR attributes from the callee prototype if we have one.
  AddAttributesFromFunctionProtoType(getContext(), FuncAttrs,
                                     CalleeInfo.getCalleeFunctionProtoType());

  const Decl *TargetDecl = CalleeInfo.getCalleeDecl().getDecl();

  bool HasOptnone = false;
  // The NoBuiltinAttr attached to the target FunctionDecl.
  const NoBuiltinAttr *NBA = nullptr;

  // Collect function IR attributes based on declaration-specific
  // information.
  // FIXME: handle sseregparm someday...
  if (TargetDecl) {
    if (TargetDecl->hasAttr<ReturnsTwiceAttr>())
      FuncAttrs.addAttribute(llvm::Attribute::ReturnsTwice);
    if (TargetDecl->hasAttr<NoThrowAttr>())
      FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
    if (TargetDecl->hasAttr<NoReturnAttr>())
      FuncAttrs.addAttribute(llvm::Attribute::NoReturn);
    if (TargetDecl->hasAttr<ColdAttr>())
      FuncAttrs.addAttribute(llvm::Attribute::Cold);
    if (TargetDecl->hasAttr<NoDuplicateAttr>())
      FuncAttrs.addAttribute(llvm::Attribute::NoDuplicate);
    if (TargetDecl->hasAttr<ConvergentAttr>())
      FuncAttrs.addAttribute(llvm::Attribute::Convergent);

    if (const FunctionDecl *Fn = dyn_cast<FunctionDecl>(TargetDecl)) {
      AddAttributesFromFunctionProtoType(
          getContext(), FuncAttrs, Fn->getType()->getAs<FunctionProtoType>());
      if (AttrOnCallSite && Fn->isReplaceableGlobalAllocationFunction()) {
        // A sane operator new returns a non-aliasing pointer.
        auto Kind = Fn->getDeclName().getCXXOverloadedOperator();
        if (getCodeGenOpts().AssumeSaneOperatorNew &&
            (Kind == OO_New || Kind == OO_Array_New))
          RetAttrs.addAttribute(llvm::Attribute::NoAlias);
      }
      const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(Fn);
      const bool IsVirtualCall = MD && MD->isVirtual();
      // Don't use [[noreturn]], _Noreturn or [[no_builtin]] for a call to a
      // virtual function. These attributes are not inherited by overloads.
      if (!(AttrOnCallSite && IsVirtualCall)) {
        if (Fn->isNoReturn())
          FuncAttrs.addAttribute(llvm::Attribute::NoReturn);
        NBA = Fn->getAttr<NoBuiltinAttr>();
      }
    }

    // 'const', 'pure' and 'noalias' attributed functions are also nounwind.
    if (TargetDecl->hasAttr<ConstAttr>()) {
      FuncAttrs.addAttribute(llvm::Attribute::ReadNone);
      FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
    } else if (TargetDecl->hasAttr<PureAttr>()) {
      FuncAttrs.addAttribute(llvm::Attribute::ReadOnly);
      FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
    } else if (TargetDecl->hasAttr<NoAliasAttr>()) {
      FuncAttrs.addAttribute(llvm::Attribute::ArgMemOnly);
      FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
    }
    if (TargetDecl->hasAttr<RestrictAttr>())
      RetAttrs.addAttribute(llvm::Attribute::NoAlias);
    if (TargetDecl->hasAttr<ReturnsNonNullAttr>() &&
        !CodeGenOpts.NullPointerIsValid)
      RetAttrs.addAttribute(llvm::Attribute::NonNull);
    if (TargetDecl->hasAttr<AnyX86NoCallerSavedRegistersAttr>())
      FuncAttrs.addAttribute("no_caller_saved_registers");
    if (TargetDecl->hasAttr<AnyX86NoCfCheckAttr>())
      FuncAttrs.addAttribute(llvm::Attribute::NoCfCheck);

    HasOptnone = TargetDecl->hasAttr<OptimizeNoneAttr>();
    if (auto *AllocSize = TargetDecl->getAttr<AllocSizeAttr>()) {
      Optional<unsigned> NumElemsParam;
      if (AllocSize->getNumElemsParam().isValid())
        NumElemsParam = AllocSize->getNumElemsParam().getLLVMIndex();
      FuncAttrs.addAllocSizeAttr(AllocSize->getElemSizeParam().getLLVMIndex(),
                                 NumElemsParam);
    }

    if (TargetDecl->hasAttr<OpenCLKernelAttr>()) {
      if (getLangOpts().OpenCLVersion <= 120) {
        // OpenCL v1.2 Work groups are always uniform
        FuncAttrs.addAttribute("uniform-work-group-size", "true");
      } else {
        // OpenCL v2.0 Work groups may be whether uniform or not.
        // '-cl-uniform-work-group-size' compile option gets a hint
        // to the compiler that the global work-size be a multiple of
        // the work-group size specified to clEnqueueNDRangeKernel
        // (i.e. work groups are uniform).
        FuncAttrs.addAttribute("uniform-work-group-size",
                               llvm::toStringRef(CodeGenOpts.UniformWGSize));
      }
    }
  }

  // Attach "no-builtins" attributes to:
  // * call sites: both `nobuiltin` and "no-builtins" or "no-builtin-<name>".
  // * definitions: "no-builtins" or "no-builtin-<name>" only.
  // The attributes can come from:
  // * LangOpts: -ffreestanding, -fno-builtin, -fno-builtin-<name>
  // * FunctionDecl attributes: __attribute__((no_builtin(...)))
  addNoBuiltinAttributes(FuncAttrs, getLangOpts(), NBA);

  // Collect function IR attributes based on global settiings.
  getDefaultFunctionAttributes(Name, HasOptnone, AttrOnCallSite, FuncAttrs);

  // Override some default IR attributes based on declaration-specific
  // information.
  if (TargetDecl) {
    if (TargetDecl->hasAttr<NoSpeculativeLoadHardeningAttr>())
      FuncAttrs.removeAttribute(llvm::Attribute::SpeculativeLoadHardening);
    if (TargetDecl->hasAttr<SpeculativeLoadHardeningAttr>())
      FuncAttrs.addAttribute(llvm::Attribute::SpeculativeLoadHardening);
    if (TargetDecl->hasAttr<NoSplitStackAttr>())
      FuncAttrs.removeAttribute("split-stack");

    // Add NonLazyBind attribute to function declarations when -fno-plt
    // is used.
    // FIXME: what if we just haven't processed the function definition
    // yet, or if it's an external definition like C99 inline?
    if (CodeGenOpts.NoPLT) {
      if (auto *Fn = dyn_cast<FunctionDecl>(TargetDecl)) {
        if (!Fn->isDefined() && !AttrOnCallSite) {
          FuncAttrs.addAttribute(llvm::Attribute::NonLazyBind);
        }
      }
    }
  }

  // Collect non-call-site function IR attributes from declaration-specific
  // information.
  if (!AttrOnCallSite) {
    if (TargetDecl && TargetDecl->hasAttr<CmseNSEntryAttr>())
      FuncAttrs.addAttribute("cmse_nonsecure_entry");

    // Whether tail calls are enabled.
    auto shouldDisableTailCalls = [&] {
      // Should this be honored in getDefaultFunctionAttributes?
      if (CodeGenOpts.DisableTailCalls)
        return true;

      if (!TargetDecl)
        return false;

      if (TargetDecl->hasAttr<DisableTailCallsAttr>() ||
          TargetDecl->hasAttr<AnyX86InterruptAttr>())
        return true;

      if (CodeGenOpts.NoEscapingBlockTailCalls) {
        if (const auto *BD = dyn_cast<BlockDecl>(TargetDecl))
          if (!BD->doesNotEscape())
            return true;
      }

      return false;
    };
    FuncAttrs.addAttribute("disable-tail-calls",
                           llvm::toStringRef(shouldDisableTailCalls()));

    // CPU/feature overrides.  addDefaultFunctionDefinitionAttributes
    // handles these separately to set them based on the global defaults.
    GetCPUAndFeaturesAttributes(CalleeInfo.getCalleeDecl(), FuncAttrs);
  }

  // Collect attributes from arguments and return values.
  ClangToLLVMArgMapping IRFunctionArgs(getContext(), FI);

  QualType RetTy = FI.getReturnType();
  const ABIArgInfo &RetAI = FI.getReturnInfo();
  switch (RetAI.getKind()) {
  case ABIArgInfo::Extend:
    if (RetAI.isSignExt())
      RetAttrs.addAttribute(llvm::Attribute::SExt);
    else
      RetAttrs.addAttribute(llvm::Attribute::ZExt);
    LLVM_FALLTHROUGH;
  case ABIArgInfo::Direct:
    if (RetAI.getInReg())
      RetAttrs.addAttribute(llvm::Attribute::InReg);
    break;
  case ABIArgInfo::Ignore:
    break;

  case ABIArgInfo::InAlloca:
  case ABIArgInfo::Indirect: {
    // inalloca and sret disable readnone and readonly
    FuncAttrs.removeAttribute(llvm::Attribute::ReadOnly)
      .removeAttribute(llvm::Attribute::ReadNone);
    break;
  }

  case ABIArgInfo::CoerceAndExpand:
    break;

  case ABIArgInfo::Expand:
  case ABIArgInfo::IndirectAliased:
    llvm_unreachable("Invalid ABI kind for return argument");
  }

  if (const auto *RefTy = RetTy->getAs<ReferenceType>()) {
    QualType PTy = RefTy->getPointeeType();
    if (!PTy->isIncompleteType() && PTy->isConstantSizeType())
      RetAttrs.addDereferenceableAttr(
          getMinimumObjectSize(PTy).getQuantity());
    if (getContext().getTargetAddressSpace(PTy) == 0 &&
        !CodeGenOpts.NullPointerIsValid)
      RetAttrs.addAttribute(llvm::Attribute::NonNull);
    if (PTy->isObjectType()) {
      llvm::Align Alignment =
          getNaturalPointeeTypeAlignment(RetTy).getAsAlign();
      RetAttrs.addAlignmentAttr(Alignment);
    }
  }

  bool hasUsedSRet = false;
  SmallVector<llvm::AttributeSet, 4> ArgAttrs(IRFunctionArgs.totalIRArgs());

  // Attach attributes to sret.
  if (IRFunctionArgs.hasSRetArg()) {
    llvm::AttrBuilder SRETAttrs;
    SRETAttrs.addStructRetAttr(getTypes().ConvertTypeForMem(RetTy));
    hasUsedSRet = true;
    if (RetAI.getInReg())
      SRETAttrs.addAttribute(llvm::Attribute::InReg);
    SRETAttrs.addAlignmentAttr(RetAI.getIndirectAlign().getQuantity());
    ArgAttrs[IRFunctionArgs.getSRetArgNo()] =
        llvm::AttributeSet::get(getLLVMContext(), SRETAttrs);
  }

  // Attach attributes to inalloca argument.
  if (IRFunctionArgs.hasInallocaArg()) {
    llvm::AttrBuilder Attrs;
    Attrs.addAttribute(llvm::Attribute::InAlloca);
    ArgAttrs[IRFunctionArgs.getInallocaArgNo()] =
        llvm::AttributeSet::get(getLLVMContext(), Attrs);
  }

  // Apply `nonnull` and `dereferencable(N)` to the `this` argument.
  if (FI.isInstanceMethod() && !IRFunctionArgs.hasInallocaArg() &&
      !FI.arg_begin()->type->isVoidPointerType()) {
    auto IRArgs = IRFunctionArgs.getIRArgs(0);

    assert(IRArgs.second == 1 && "Expected only a single `this` pointer.");

    llvm::AttrBuilder Attrs;

    if (!CodeGenOpts.NullPointerIsValid &&
        getContext().getTargetAddressSpace(FI.arg_begin()->type) == 0) {
      Attrs.addAttribute(llvm::Attribute::NonNull);
      Attrs.addDereferenceableAttr(
          getMinimumObjectSize(
              FI.arg_begin()->type.castAs<PointerType>()->getPointeeType())
              .getQuantity());
    } else {
      // FIXME dereferenceable should be correct here, regardless of
      // NullPointerIsValid. However, dereferenceable currently does not always
      // respect NullPointerIsValid and may imply nonnull and break the program.
      // See https://reviews.llvm.org/D66618 for discussions.
      Attrs.addDereferenceableOrNullAttr(
          getMinimumObjectSize(
              FI.arg_begin()->type.castAs<PointerType>()->getPointeeType())
              .getQuantity());
    }

    ArgAttrs[IRArgs.first] = llvm::AttributeSet::get(getLLVMContext(), Attrs);
  }

  unsigned ArgNo = 0;
  for (CGFunctionInfo::const_arg_iterator I = FI.arg_begin(),
                                          E = FI.arg_end();
       I != E; ++I, ++ArgNo) {
    QualType ParamType = I->type;
    const ABIArgInfo &AI = I->info;
    llvm::AttrBuilder Attrs;

    // Add attribute for padding argument, if necessary.
    if (IRFunctionArgs.hasPaddingArg(ArgNo)) {
      if (AI.getPaddingInReg()) {
        ArgAttrs[IRFunctionArgs.getPaddingArgNo(ArgNo)] =
            llvm::AttributeSet::get(
                getLLVMContext(),
                llvm::AttrBuilder().addAttribute(llvm::Attribute::InReg));
      }
    }

    // 'restrict' -> 'noalias' is done in EmitFunctionProlog when we
    // have the corresponding parameter variable.  It doesn't make
    // sense to do it here because parameters are so messed up.
    switch (AI.getKind()) {
    case ABIArgInfo::Extend:
      if (AI.isSignExt())
        Attrs.addAttribute(llvm::Attribute::SExt);
      else
        Attrs.addAttribute(llvm::Attribute::ZExt);
      LLVM_FALLTHROUGH;
    case ABIArgInfo::Direct:
      if (ArgNo == 0 && FI.isChainCall())
        Attrs.addAttribute(llvm::Attribute::Nest);
      else if (AI.getInReg())
        Attrs.addAttribute(llvm::Attribute::InReg);
      break;

    case ABIArgInfo::Indirect: {
      if (AI.getInReg())
        Attrs.addAttribute(llvm::Attribute::InReg);

      if (AI.getIndirectByVal())
        Attrs.addByValAttr(getTypes().ConvertTypeForMem(ParamType));

      auto *Decl = ParamType->getAsRecordDecl();
      if (CodeGenOpts.PassByValueIsNoAlias && Decl &&
          Decl->getArgPassingRestrictions() == RecordDecl::APK_CanPassInRegs)
        // When calling the function, the pointer passed in will be the only
        // reference to the underlying object. Mark it accordingly.
        Attrs.addAttribute(llvm::Attribute::NoAlias);

      // TODO: We could add the byref attribute if not byval, but it would
      // require updating many testcases.

      CharUnits Align = AI.getIndirectAlign();

      // In a byval argument, it is important that the required
      // alignment of the type is honored, as LLVM might be creating a
      // *new* stack object, and needs to know what alignment to give
      // it. (Sometimes it can deduce a sensible alignment on its own,
      // but not if clang decides it must emit a packed struct, or the
      // user specifies increased alignment requirements.)
      //
      // This is different from indirect *not* byval, where the object
      // exists already, and the align attribute is purely
      // informative.
      assert(!Align.isZero());

      // For now, only add this when we have a byval argument.
      // TODO: be less lazy about updating test cases.
      if (AI.getIndirectByVal())
        Attrs.addAlignmentAttr(Align.getQuantity());

      // byval disables readnone and readonly.
      FuncAttrs.removeAttribute(llvm::Attribute::ReadOnly)
        .removeAttribute(llvm::Attribute::ReadNone);

      break;
    }
    case ABIArgInfo::IndirectAliased: {
      CharUnits Align = AI.getIndirectAlign();
      Attrs.addByRefAttr(getTypes().ConvertTypeForMem(ParamType));
      Attrs.addAlignmentAttr(Align.getQuantity());
      break;
    }
    case ABIArgInfo::Ignore:
    case ABIArgInfo::Expand:
    case ABIArgInfo::CoerceAndExpand:
      break;

    case ABIArgInfo::InAlloca:
      // inalloca disables readnone and readonly.
      FuncAttrs.removeAttribute(llvm::Attribute::ReadOnly)
          .removeAttribute(llvm::Attribute::ReadNone);
      continue;
    }

    if (const auto *RefTy = ParamType->getAs<ReferenceType>()) {
      QualType PTy = RefTy->getPointeeType();
      if (!PTy->isIncompleteType() && PTy->isConstantSizeType())
        Attrs.addDereferenceableAttr(
            getMinimumObjectSize(PTy).getQuantity());
      if (getContext().getTargetAddressSpace(PTy) == 0 &&
          !CodeGenOpts.NullPointerIsValid)
        Attrs.addAttribute(llvm::Attribute::NonNull);
      if (PTy->isObjectType()) {
        llvm::Align Alignment =
            getNaturalPointeeTypeAlignment(ParamType).getAsAlign();
        Attrs.addAlignmentAttr(Alignment);
      }
    }

    switch (FI.getExtParameterInfo(ArgNo).getABI()) {
    case ParameterABI::Ordinary:
      break;

    case ParameterABI::SwiftIndirectResult: {
      // Add 'sret' if we haven't already used it for something, but
      // only if the result is void.
      if (!hasUsedSRet && RetTy->isVoidType()) {
        Attrs.addStructRetAttr(getTypes().ConvertTypeForMem(ParamType));
        hasUsedSRet = true;
      }

      // Add 'noalias' in either case.
      Attrs.addAttribute(llvm::Attribute::NoAlias);

      // Add 'dereferenceable' and 'alignment'.
      auto PTy = ParamType->getPointeeType();
      if (!PTy->isIncompleteType() && PTy->isConstantSizeType()) {
        auto info = getContext().getTypeInfoInChars(PTy);
        Attrs.addDereferenceableAttr(info.Width.getQuantity());
        Attrs.addAlignmentAttr(info.Align.getAsAlign());
      }
      break;
    }

    case ParameterABI::SwiftErrorResult:
      Attrs.addAttribute(llvm::Attribute::SwiftError);
      break;

    case ParameterABI::SwiftContext:
      Attrs.addAttribute(llvm::Attribute::SwiftSelf);
      break;
    }

    if (FI.getExtParameterInfo(ArgNo).isNoEscape())
      Attrs.addAttribute(llvm::Attribute::NoCapture);

    if (Attrs.hasAttributes()) {
      unsigned FirstIRArg, NumIRArgs;
      std::tie(FirstIRArg, NumIRArgs) = IRFunctionArgs.getIRArgs(ArgNo);
      for (unsigned i = 0; i < NumIRArgs; i++)
        ArgAttrs[FirstIRArg + i] =
            llvm::AttributeSet::get(getLLVMContext(), Attrs);
    }
  }
  assert(ArgNo == FI.arg_size());

  AttrList = llvm::AttributeList::get(
      getLLVMContext(), llvm::AttributeSet::get(getLLVMContext(), FuncAttrs),
      llvm::AttributeSet::get(getLLVMContext(), RetAttrs), ArgAttrs);
}

/// An argument came in as a promoted argument; demote it back to its
/// declared type.
static llvm::Value *emitArgumentDemotion(CodeGenFunction &CGF,
                                         const VarDecl *var,
                                         llvm::Value *value) {
  llvm::Type *varType = CGF.ConvertType(var->getType());

  // This can happen with promotions that actually don't change the
  // underlying type, like the enum promotions.
  if (value->getType() == varType) return value;

  assert((varType->isIntegerTy() || varType->isFloatingPointTy())
         && "unexpected promotion type");

  if (isa<llvm::IntegerType>(varType))
    return CGF.Builder.CreateTrunc(value, varType, "arg.unpromote");

  return CGF.Builder.CreateFPCast(value, varType, "arg.unpromote");
}

/// Returns the attribute (either parameter attribute, or function
/// attribute), which declares argument ArgNo to be non-null.
static const NonNullAttr *getNonNullAttr(const Decl *FD, const ParmVarDecl *PVD,
                                         QualType ArgType, unsigned ArgNo) {
  // FIXME: __attribute__((nonnull)) can also be applied to:
  //   - references to pointers, where the pointee is known to be
  //     nonnull (apparently a Clang extension)
  //   - transparent unions containing pointers
  // In the former case, LLVM IR cannot represent the constraint. In
  // the latter case, we have no guarantee that the transparent union
  // is in fact passed as a pointer.
  if (!ArgType->isAnyPointerType() && !ArgType->isBlockPointerType())
    return nullptr;
  // First, check attribute on parameter itself.
  if (PVD) {
    if (auto ParmNNAttr = PVD->getAttr<NonNullAttr>())
      return ParmNNAttr;
  }
  // Check function attributes.
  if (!FD)
    return nullptr;
  for (const auto *NNAttr : FD->specific_attrs<NonNullAttr>()) {
    if (NNAttr->isNonNull(ArgNo))
      return NNAttr;
  }
  return nullptr;
}

namespace {
  struct CopyBackSwiftError final : EHScopeStack::Cleanup {
    Address Temp;
    Address Arg;
    CopyBackSwiftError(Address temp, Address arg) : Temp(temp), Arg(arg) {}
    void Emit(CodeGenFunction &CGF, Flags flags) override {
      llvm::Value *errorValue = CGF.Builder.CreateLoad(Temp);
      CGF.Builder.CreateStore(errorValue, Arg);
    }
  };
}

void CodeGenFunction::EmitFunctionProlog(const CGFunctionInfo &FI,
                                         llvm::Function *Fn,
                                         const FunctionArgList &Args) {
  if (CurCodeDecl && CurCodeDecl->hasAttr<NakedAttr>())
    // Naked functions don't have prologues.
    return;

  // 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>(CurCodeDecl)) {
    if (FD->hasImplicitReturnZero()) {
      QualType RetTy = FD->getReturnType().getUnqualifiedType();
      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.

  ClangToLLVMArgMapping IRFunctionArgs(CGM.getContext(), FI);
  assert(Fn->arg_size() == IRFunctionArgs.totalIRArgs());

  // If we're using inalloca, all the memory arguments are GEPs off of the last
  // parameter, which is a pointer to the complete memory area.
  Address ArgStruct = Address::invalid();
  if (IRFunctionArgs.hasInallocaArg()) {
    ArgStruct = Address(Fn->getArg(IRFunctionArgs.getInallocaArgNo()),
                        FI.getArgStructAlignment());

    assert(ArgStruct.getType() == FI.getArgStruct()->getPointerTo());
  }

  // Name the struct return parameter.
  if (IRFunctionArgs.hasSRetArg()) {
    auto AI = Fn->getArg(IRFunctionArgs.getSRetArgNo());
    AI->setName("agg.result");
    AI->addAttr(llvm::Attribute::NoAlias);
  }

  // Track if we received the parameter as a pointer (indirect, byval, or
  // inalloca).  If already have a pointer, EmitParmDecl doesn't need to copy it
  // into a local alloca for us.
  SmallVector<ParamValue, 16> ArgVals;
  ArgVals.reserve(Args.size());

  // Create a pointer value for every parameter declaration.  This usually
  // entails copying one or more LLVM IR arguments into an alloca.  Don't push
  // any cleanups or do anything that might unwind.  We do that separately, so
  // we can push the cleanups in the correct order for the ABI.
  assert(FI.arg_size() == Args.size() &&
         "Mismatch between function signature & arguments.");
  unsigned ArgNo = 0;
  CGFunctionInfo::const_arg_iterator info_it = FI.arg_begin();
  for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
       i != e; ++i, ++info_it, ++ArgNo) {
    const VarDecl *Arg = *i;
    const ABIArgInfo &ArgI = info_it->info;

    bool isPromoted =
      isa<ParmVarDecl>(Arg) && cast<ParmVarDecl>(Arg)->isKNRPromoted();
    // We are converting from ABIArgInfo type to VarDecl type directly, unless
    // the parameter is promoted. In this case we convert to
    // CGFunctionInfo::ArgInfo type with subsequent argument demotion.
    QualType Ty = isPromoted ? info_it->type : Arg->getType();
    assert(hasScalarEvaluationKind(Ty) ==
           hasScalarEvaluationKind(Arg->getType()));

    unsigned FirstIRArg, NumIRArgs;
    std::tie(FirstIRArg, NumIRArgs) = IRFunctionArgs.getIRArgs(ArgNo);

    switch (ArgI.getKind()) {
    case ABIArgInfo::InAlloca: {
      assert(NumIRArgs == 0);
      auto FieldIndex = ArgI.getInAllocaFieldIndex();
      Address V =
          Builder.CreateStructGEP(ArgStruct, FieldIndex, Arg->getName());
      if (ArgI.getInAllocaIndirect())
        V = Address(Builder.CreateLoad(V),
                    getContext().getTypeAlignInChars(Ty));
      ArgVals.push_back(ParamValue::forIndirect(V));
      break;
    }

    case ABIArgInfo::Indirect:
    case ABIArgInfo::IndirectAliased: {
      assert(NumIRArgs == 1);
      Address ParamAddr =
          Address(Fn->getArg(FirstIRArg), ArgI.getIndirectAlign());

      if (!hasScalarEvaluationKind(Ty)) {
        // Aggregates and complex variables are accessed by reference. All we
        // need to do is realign the value, if requested. Also, if the address
        // may be aliased, copy it to ensure that the parameter variable is
        // mutable and has a unique adress, as C requires.
        Address V = ParamAddr;
        if (ArgI.getIndirectRealign() || ArgI.isIndirectAliased()) {
          Address AlignedTemp = CreateMemTemp(Ty, "coerce");

          // Copy from the incoming argument pointer to the temporary with the
          // appropriate alignment.
          //
          // FIXME: We should have a common utility for generating an aggregate
          // copy.
          CharUnits Size = getContext().getTypeSizeInChars(Ty);
          Builder.CreateMemCpy(
              AlignedTemp.getPointer(), AlignedTemp.getAlignment().getAsAlign(),
              ParamAddr.getPointer(), ParamAddr.getAlignment().getAsAlign(),
              llvm::ConstantInt::get(IntPtrTy, Size.getQuantity()));
          V = AlignedTemp;
        }
        ArgVals.push_back(ParamValue::forIndirect(V));
      } else {
        // Load scalar value from indirect argument.
        llvm::Value *V =
            EmitLoadOfScalar(ParamAddr, false, Ty, Arg->getBeginLoc());

        if (isPromoted)
          V = emitArgumentDemotion(*this, Arg, V);
        ArgVals.push_back(ParamValue::forDirect(V));
      }
      break;
    }

    case ABIArgInfo::Extend:
    case ABIArgInfo::Direct: {
      auto AI = Fn->getArg(FirstIRArg);
      llvm::Type *LTy = ConvertType(Arg->getType());

      // Prepare parameter attributes. So far, only attributes for pointer
      // parameters are prepared. See
      // http://llvm.org/docs/LangRef.html#paramattrs.
      if (ArgI.getDirectOffset() == 0 && LTy->isPointerTy() &&
          ArgI.getCoerceToType()->isPointerTy()) {
        assert(NumIRArgs == 1);

        if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(Arg)) {
          // Set `nonnull` attribute if any.
          if (getNonNullAttr(CurCodeDecl, PVD, PVD->getType(),
                             PVD->getFunctionScopeIndex()) &&
              !CGM.getCodeGenOpts().NullPointerIsValid)
            AI->addAttr(llvm::Attribute::NonNull);

          QualType OTy = PVD->getOriginalType();
          if (const auto *ArrTy =
              getContext().getAsConstantArrayType(OTy)) {
            // A C99 array parameter declaration with the static keyword also
            // indicates dereferenceability, and if the size is constant we can
            // use the dereferenceable attribute (which requires the size in
            // bytes).
            if (ArrTy->getSizeModifier() == ArrayType::Static) {
              QualType ETy = ArrTy->getElementType();
              llvm::Align Alignment =
                  CGM.getNaturalTypeAlignment(ETy).getAsAlign();
              AI->addAttrs(llvm::AttrBuilder().addAlignmentAttr(Alignment));
              uint64_t ArrSize = ArrTy->getSize().getZExtValue();
              if (!ETy->isIncompleteType() && ETy->isConstantSizeType() &&
                  ArrSize) {
                llvm::AttrBuilder Attrs;
                Attrs.addDereferenceableAttr(
                    getContext().getTypeSizeInChars(ETy).getQuantity() *
                    ArrSize);
                AI->addAttrs(Attrs);
              } else if (getContext().getTargetInfo().getNullPointerValue(
                             ETy.getAddressSpace()) == 0 &&
                         !CGM.getCodeGenOpts().NullPointerIsValid) {
                AI->addAttr(llvm::Attribute::NonNull);
              }
            }
          } else if (const auto *ArrTy =
                     getContext().getAsVariableArrayType(OTy)) {
            // For C99 VLAs with the static keyword, we don't know the size so
            // we can't use the dereferenceable attribute, but in addrspace(0)
            // we know that it must be nonnull.
            if (ArrTy->getSizeModifier() == VariableArrayType::Static) {
              QualType ETy = ArrTy->getElementType();
              llvm::Align Alignment =
                  CGM.getNaturalTypeAlignment(ETy).getAsAlign();
              AI->addAttrs(llvm::AttrBuilder().addAlignmentAttr(Alignment));
              if (!getContext().getTargetAddressSpace(ETy) &&
                  !CGM.getCodeGenOpts().NullPointerIsValid)
                AI->addAttr(llvm::Attribute::NonNull);
            }
          }

          // Set `align` attribute if any.
          const auto *AVAttr = PVD->getAttr<AlignValueAttr>();
          if (!AVAttr)
            if (const auto *TOTy = dyn_cast<TypedefType>(OTy))
              AVAttr = TOTy->getDecl()->getAttr<AlignValueAttr>();
          if (AVAttr && !SanOpts.has(SanitizerKind::Alignment)) {
            // If alignment-assumption sanitizer is enabled, we do *not* add
            // alignment attribute here, but emit normal alignment assumption,
            // so the UBSAN check could function.
            llvm::ConstantInt *AlignmentCI =
                cast<llvm::ConstantInt>(EmitScalarExpr(AVAttr->getAlignment()));
            unsigned AlignmentInt =
                AlignmentCI->getLimitedValue(llvm::Value::MaximumAlignment);
            if (AI->getParamAlign().valueOrOne() < AlignmentInt) {
              AI->removeAttr(llvm::Attribute::AttrKind::Alignment);
              AI->addAttrs(llvm::AttrBuilder().addAlignmentAttr(
                  llvm::Align(AlignmentInt)));
            }
          }
        }

        // Set 'noalias' if an argument type has the `restrict` qualifier.
        if (Arg->getType().isRestrictQualified())
          AI->addAttr(llvm::Attribute::NoAlias);
      }

      // Prepare the argument value. If we have the trivial case, handle it
      // with no muss and fuss.
      if (!isa<llvm::StructType>(ArgI.getCoerceToType()) &&
          ArgI.getCoerceToType() == ConvertType(Ty) &&
          ArgI.getDirectOffset() == 0) {
        assert(NumIRArgs == 1);

        // LLVM expects swifterror parameters to be used in very restricted
        // ways.  Copy the value into a less-restricted temporary.
        llvm::Value *V = AI;
        if (FI.getExtParameterInfo(ArgNo).getABI()
              == ParameterABI::SwiftErrorResult) {
          QualType pointeeTy = Ty->getPointeeType();
          assert(pointeeTy->isPointerType());
          Address temp =
            CreateMemTemp(pointeeTy, getPointerAlign(), "swifterror.temp");
          Address arg = Address(V, getContext().getTypeAlignInChars(pointeeTy));
          llvm::Value *incomingErrorValue = Builder.CreateLoad(arg);
          Builder.CreateStore(incomingErrorValue, temp);
          V = temp.getPointer();

          // Push a cleanup to copy the value back at the end of the function.
          // The convention does not guarantee that the value will be written
          // back if the function exits with an unwind exception.
          EHStack.pushCleanup<CopyBackSwiftError>(NormalCleanup, temp, arg);
        }

        // Ensure the argument is the correct type.
        if (V->getType() != ArgI.getCoerceToType())
          V = Builder.CreateBitCast(V, ArgI.getCoerceToType());

        if (isPromoted)
          V = emitArgumentDemotion(*this, Arg, V);

        // Because of merging of function types from multiple decls it is
        // possible for the type of an argument to not match the corresponding
        // type in the function type. Since we are codegening the callee
        // in here, add a cast to the argument type.
        llvm::Type *LTy = ConvertType(Arg->getType());
        if (V->getType() != LTy)
          V = Builder.CreateBitCast(V, LTy);

        ArgVals.push_back(ParamValue::forDirect(V));
        break;
      }

      Address Alloca = CreateMemTemp(Ty, getContext().getDeclAlign(Arg),
                                     Arg->getName());

      // Pointer to store into.
      Address Ptr = emitAddressAtOffset(*this, Alloca, ArgI);

      // Fast-isel and the optimizer generally like scalar values better than
      // FCAs, so we flatten them if this is safe to do for this argument.
      llvm::StructType *STy = dyn_cast<llvm::StructType>(ArgI.getCoerceToType());
      if (ArgI.isDirect() && ArgI.getCanBeFlattened() && STy &&
          STy->getNumElements() > 1) {
        uint64_t SrcSize = CGM.getDataLayout().getTypeAllocSize(STy);
        llvm::Type *DstTy = Ptr.getElementType();
        uint64_t DstSize = CGM.getDataLayout().getTypeAllocSize(DstTy);

        Address AddrToStoreInto = Address::invalid();
        if (SrcSize <= DstSize) {
          AddrToStoreInto = Builder.CreateElementBitCast(Ptr, STy);
        } else {
          AddrToStoreInto =
            CreateTempAlloca(STy, Alloca.getAlignment(), "coerce");
        }

        assert(STy->getNumElements() == NumIRArgs);
        for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
          auto AI = Fn->getArg(FirstIRArg + i);
          AI->setName(Arg->getName() + ".coerce" + Twine(i));
          Address EltPtr = Builder.CreateStructGEP(AddrToStoreInto, i);
          Builder.CreateStore(AI, EltPtr);
        }

        if (SrcSize > DstSize) {
          Builder.CreateMemCpy(Ptr, AddrToStoreInto, DstSize);
        }

      } else {
        // Simple case, just do a coerced store of the argument into the alloca.
        assert(NumIRArgs == 1);
        auto AI = Fn->getArg(FirstIRArg);
        AI->setName(Arg->getName() + ".coerce");
        CreateCoercedStore(AI, Ptr, /*DstIsVolatile=*/false, *this);
      }

      // Match to what EmitParmDecl is expecting for this type.
      if (CodeGenFunction::hasScalarEvaluationKind(Ty)) {
        llvm::Value *V =
            EmitLoadOfScalar(Alloca, false, Ty, Arg->getBeginLoc());
        if (isPromoted)
          V = emitArgumentDemotion(*this, Arg, V);
        ArgVals.push_back(ParamValue::forDirect(V));
      } else {
        ArgVals.push_back(ParamValue::forIndirect(Alloca));
      }
      break;
    }

    case ABIArgInfo::CoerceAndExpand: {
      // Reconstruct into a temporary.
      Address alloca = CreateMemTemp(Ty, getContext().getDeclAlign(Arg));
      ArgVals.push_back(ParamValue::forIndirect(alloca));

      auto coercionType = ArgI.getCoerceAndExpandType();
      alloca = Builder.CreateElementBitCast(alloca, coercionType);

      unsigned argIndex = FirstIRArg;
      for (unsigned i = 0, e = coercionType->getNumElements(); i != e; ++i) {
        llvm::Type *eltType = coercionType->getElementType(i);
        if (ABIArgInfo::isPaddingForCoerceAndExpand(eltType))
          continue;

        auto eltAddr = Builder.CreateStructGEP(alloca, i);
        auto elt = Fn->getArg(argIndex++);
        Builder.CreateStore(elt, eltAddr);
      }
      assert(argIndex == FirstIRArg + NumIRArgs);
      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.
      Address Alloca = CreateMemTemp(Ty, getContext().getDeclAlign(Arg));
      LValue LV = MakeAddrLValue(Alloca, Ty);
      ArgVals.push_back(ParamValue::forIndirect(Alloca));

      auto FnArgIter = Fn->arg_begin() + FirstIRArg;
      ExpandTypeFromArgs(Ty, LV, FnArgIter);
      assert(FnArgIter == Fn->arg_begin() + FirstIRArg + NumIRArgs);
      for (unsigned i = 0, e = NumIRArgs; i != e; ++i) {
        auto AI = Fn->getArg(FirstIRArg + i);
        AI->setName(Arg->getName() + "." + Twine(i));
      }
      break;
    }

    case ABIArgInfo::Ignore:
      assert(NumIRArgs == 0);
      // Initialize the local variable appropriately.
      if (!hasScalarEvaluationKind(Ty)) {
        ArgVals.push_back(ParamValue::forIndirect(CreateMemTemp(Ty)));
      } else {
        llvm::Value *U = llvm::UndefValue::get(ConvertType(Arg->getType()));
        ArgVals.push_back(ParamValue::forDirect(U));
      }
      break;
    }
  }

  if (getTarget().getCXXABI().areArgsDestroyedLeftToRightInCallee()) {
    for (int I = Args.size() - 1; I >= 0; --I)
      EmitParmDecl(*Args[I], ArgVals[I], I + 1);
  } else {
    for (unsigned I = 0, E = Args.size(); I != E; ++I)
      EmitParmDecl(*Args[I], ArgVals[I], I + 1);
  }
}

static void eraseUnusedBitCasts(llvm::Instruction *insn) {
  while (insn->use_empty()) {
    llvm::BitCastInst *bitcast = dyn_cast<llvm::BitCastInst>(insn);
    if (!bitcast) return;

    // This is "safe" because we would have used a ConstantExpr otherwise.
    insn = cast<llvm::Instruction>(bitcast->getOperand(0));
    bitcast->eraseFromParent();
  }
}

/// Try to emit a fused autorelease of a return result.
static llvm::Value *tryEmitFusedAutoreleaseOfResult(CodeGenFunction &CGF,
                                                    llvm::Value *result) {
  // We must be immediately followed the cast.
  llvm::BasicBlock *BB = CGF.Builder.GetInsertBlock();
  if (BB->empty()) return nullptr;
  if (&BB->back() != result) return nullptr;

  llvm::Type *resultType = result->getType();

  // result is in a BasicBlock and is therefore an Instruction.
  llvm::Instruction *generator = cast<llvm::Instruction>(result);

  SmallVector<llvm::Instruction *, 4> InstsToKill;

  // Look for:
  //  %generator = bitcast %type1* %generator2 to %type2*
  while (llvm::BitCastInst *bitcast = dyn_cast<llvm::BitCastInst>(generator)) {
    // We would have emitted this as a constant if the operand weren't
    // an Instruction.
    generator = cast<llvm::Instruction>(bitcast->getOperand(0));

    // Require the generator to be immediately followed by the cast.
    if (generator->getNextNode() != bitcast)
      return nullptr;

    InstsToKill.push_back(bitcast);
  }

  // Look for:
  //   %generator = call i8* @objc_retain(i8* %originalResult)
  // or
  //   %generator = call i8* @objc_retainAutoreleasedReturnValue(i8* %originalResult)
  llvm::CallInst *call = dyn_cast<llvm::CallInst>(generator);
  if (!call) return nullptr;

  bool doRetainAutorelease;

  if (call->getCalledOperand() == CGF.CGM.getObjCEntrypoints().objc_retain) {
    doRetainAutorelease = true;
  } else if (call->getCalledOperand() ==
             CGF.CGM.getObjCEntrypoints().objc_retainAutoreleasedReturnValue) {
    doRetainAutorelease = false;

    // If we emitted an assembly marker for this call (and the
    // ARCEntrypoints field should have been set if so), go looking
    // for that call.  If we can't find it, we can't do this
    // optimization.  But it should always be the immediately previous
    // instruction, unless we needed bitcasts around the call.
    if (CGF.CGM.getObjCEntrypoints().retainAutoreleasedReturnValueMarker) {
      llvm::Instruction *prev = call->getPrevNode();
      assert(prev);
      if (isa<llvm::BitCastInst>(prev)) {
        prev = prev->getPrevNode();
        assert(prev);
      }
      assert(isa<llvm::CallInst>(prev));
      assert(cast<llvm::CallInst>(prev)->getCalledOperand() ==
             CGF.CGM.getObjCEntrypoints().retainAutoreleasedReturnValueMarker);
      InstsToKill.push_back(prev);
    }
  } else {
    return nullptr;
  }

  result = call->getArgOperand(0);
  InstsToKill.push_back(call);

  // Keep killing bitcasts, for sanity.  Note that we no longer care
  // about precise ordering as long as there's exactly one use.
  while (llvm::BitCastInst *bitcast = dyn_cast<llvm::BitCastInst>(result)) {
    if (!bitcast->hasOneUse()) break;
    InstsToKill.push_back(bitcast);
    result = bitcast->getOperand(0);
  }

  // Delete all the unnecessary instructions, from latest to earliest.
  for (auto *I : InstsToKill)
    I->eraseFromParent();

  // Do the fused retain/autorelease if we were asked to.
  if (doRetainAutorelease)
    result = CGF.EmitARCRetainAutoreleaseReturnValue(result);

  // Cast back to the result type.
  return CGF.Builder.CreateBitCast(result, resultType);
}

/// If this is a +1 of the value of an immutable 'self', remove it.
static llvm::Value *tryRemoveRetainOfSelf(CodeGenFunction &CGF,
                                          llvm::Value *result) {
  // This is only applicable to a method with an immutable 'self'.
  const ObjCMethodDecl *method =
    dyn_cast_or_null<ObjCMethodDecl>(CGF.CurCodeDecl);
  if (!method) return nullptr;
  const VarDecl *self = method->getSelfDecl();
  if (!self->getType().isConstQualified()) return nullptr;

  // Look for a retain call.
  llvm::CallInst *retainCall =
    dyn_cast<llvm::CallInst>(result->stripPointerCasts());
  if (!retainCall || retainCall->getCalledOperand() !=
                         CGF.CGM.getObjCEntrypoints().objc_retain)
    return nullptr;

  // Look for an ordinary load of 'self'.
  llvm::Value *retainedValue = retainCall->getArgOperand(0);
  llvm::LoadInst *load =
    dyn_cast<llvm::LoadInst>(retainedValue->stripPointerCasts());
  if (!load || load->isAtomic() || load->isVolatile() ||
      load->getPointerOperand() != CGF.GetAddrOfLocalVar(self).getPointer())
    return nullptr;

  // Okay!  Burn it all down.  This relies for correctness on the
  // assumption that the retain is emitted as part of the return and
  // that thereafter everything is used "linearly".
  llvm::Type *resultType = result->getType();
  eraseUnusedBitCasts(cast<llvm::Instruction>(result));
  assert(retainCall->use_empty());
  retainCall->eraseFromParent();
  eraseUnusedBitCasts(cast<llvm::Instruction>(retainedValue));

  return CGF.Builder.CreateBitCast(load, resultType);
}

/// Emit an ARC autorelease of the result of a function.
///
/// \return the value to actually return from the function
static llvm::Value *emitAutoreleaseOfResult(CodeGenFunction &CGF,
                                            llvm::Value *result) {
  // If we're returning 'self', kill the initial retain.  This is a
  // heuristic attempt to "encourage correctness" in the really unfortunate
  // case where we have a return of self during a dealloc and we desperately
  // need to avoid the possible autorelease.
  if (llvm::Value *self = tryRemoveRetainOfSelf(CGF, result))
    return self;

  // At -O0, try to emit a fused retain/autorelease.
  if (CGF.shouldUseFusedARCCalls())
    if (llvm::Value *fused = tryEmitFusedAutoreleaseOfResult(CGF, result))
      return fused;

  return CGF.EmitARCAutoreleaseReturnValue(result);
}

/// Heuristically search for a dominating store to the return-value slot.
static llvm::StoreInst *findDominatingStoreToReturnValue(CodeGenFunction &CGF) {
  // Check if a User is a store which pointerOperand is the ReturnValue.
  // We are looking for stores to the ReturnValue, not for stores of the
  // ReturnValue to some other location.
  auto GetStoreIfValid = [&CGF](llvm::User *U) -> llvm::StoreInst * {
    auto *SI = dyn_cast<llvm::StoreInst>(U);
    if (!SI || SI->getPointerOperand() != CGF.ReturnValue.getPointer())
      return nullptr;
    // These aren't actually possible for non-coerced returns, and we
    // only care about non-coerced returns on this code path.
    assert(!SI->isAtomic() && !SI->isVolatile());
    return SI;
  };
  // If there are multiple uses of the return-value slot, just check
  // for something immediately preceding the IP.  Sometimes this can
  // happen with how we generate implicit-returns; it can also happen
  // with noreturn cleanups.
  if (!CGF.ReturnValue.getPointer()->hasOneUse()) {
    llvm::BasicBlock *IP = CGF.Builder.GetInsertBlock();
    if (IP->empty()) return nullptr;
    llvm::Instruction *I = &IP->back();

    // Skip lifetime markers
    for (llvm::BasicBlock::reverse_iterator II = IP->rbegin(),
                                            IE = IP->rend();
         II != IE; ++II) {
      if (llvm::IntrinsicInst *Intrinsic =
              dyn_cast<llvm::IntrinsicInst>(&*II)) {
        if (Intrinsic->getIntrinsicID() == llvm::Intrinsic::lifetime_end) {
          const llvm::Value *CastAddr = Intrinsic->getArgOperand(1);
          ++II;
          if (II == IE)
            break;
          if (isa<llvm::BitCastInst>(&*II) && (CastAddr == &*II))
            continue;
        }
      }
      I = &*II;
      break;
    }

    return GetStoreIfValid(I);
  }

  llvm::StoreInst *store =
      GetStoreIfValid(CGF.ReturnValue.getPointer()->user_back());
  if (!store) return nullptr;

  // Now do a first-and-dirty dominance check: just walk up the
  // single-predecessors chain from the current insertion point.
  llvm::BasicBlock *StoreBB = store->getParent();
  llvm::BasicBlock *IP = CGF.Builder.GetInsertBlock();
  while (IP != StoreBB) {
    if (!(IP = IP->getSinglePredecessor()))
      return nullptr;
  }

  // Okay, the store's basic block dominates the insertion point; we
  // can do our thing.
  return store;
}

// Helper functions for EmitCMSEClearRecord

// Set the bits corresponding to a field having width `BitWidth` and located at
// offset `BitOffset` (from the least significant bit) within a storage unit of
// `Bits.size()` bytes. Each element of `Bits` corresponds to one target byte.
// Use little-endian layout, i.e.`Bits[0]` is the LSB.
static void setBitRange(SmallVectorImpl<uint64_t> &Bits, int BitOffset,
                        int BitWidth, int CharWidth) {
  assert(CharWidth <= 64);
  assert(static_cast<unsigned>(BitWidth) <= Bits.size() * CharWidth);

  int Pos = 0;
  if (BitOffset >= CharWidth) {
    Pos += BitOffset / CharWidth;
    BitOffset = BitOffset % CharWidth;
  }

  const uint64_t Used = (uint64_t(1) << CharWidth) - 1;
  if (BitOffset + BitWidth >= CharWidth) {
    Bits[Pos++] |= (Used << BitOffset) & Used;
    BitWidth -= CharWidth - BitOffset;
    BitOffset = 0;
  }

  while (BitWidth >= CharWidth) {
    Bits[Pos++] = Used;
    BitWidth -= CharWidth;
  }

  if (BitWidth > 0)
    Bits[Pos++] |= (Used >> (CharWidth - BitWidth)) << BitOffset;
}

// Set the bits corresponding to a field having width `BitWidth` and located at
// offset `BitOffset` (from the least significant bit) within a storage unit of
// `StorageSize` bytes, located at `StorageOffset` in `Bits`. Each element of
// `Bits` corresponds to one target byte. Use target endian layout.
static void setBitRange(SmallVectorImpl<uint64_t> &Bits, int StorageOffset,
                        int StorageSize, int BitOffset, int BitWidth,
                        int CharWidth, bool BigEndian) {

  SmallVector<uint64_t, 8> TmpBits(StorageSize);
  setBitRange(TmpBits, BitOffset, BitWidth, CharWidth);

  if (BigEndian)
    std::reverse(TmpBits.begin(), TmpBits.end());

  for (uint64_t V : TmpBits)
    Bits[StorageOffset++] |= V;
}

static void setUsedBits(CodeGenModule &, QualType, int,
                        SmallVectorImpl<uint64_t> &);

// Set the bits in `Bits`, which correspond to the value representations of
// the actual members of the record type `RTy`. Note that this function does
// not handle base classes, virtual tables, etc, since they cannot happen in
// CMSE function arguments or return. The bit mask corresponds to the target
// memory layout, i.e. it's endian dependent.
static void setUsedBits(CodeGenModule &CGM, const RecordType *RTy, int Offset,
                        SmallVectorImpl<uint64_t> &Bits) {
  ASTContext &Context = CGM.getContext();
  int CharWidth = Context.getCharWidth();
  const RecordDecl *RD = RTy->getDecl()->getDefinition();
  const ASTRecordLayout &ASTLayout = Context.getASTRecordLayout(RD);
  const CGRecordLayout &Layout = CGM.getTypes().getCGRecordLayout(RD);

  int Idx = 0;
  for (auto I = RD->field_begin(), E = RD->field_end(); I != E; ++I, ++Idx) {
    const FieldDecl *F = *I;

    if (F->isUnnamedBitfield() || F->isZeroLengthBitField(Context) ||
        F->getType()->isIncompleteArrayType())
      continue;

    if (F->isBitField()) {
      const CGBitFieldInfo &BFI = Layout.getBitFieldInfo(F);
      setBitRange(Bits, Offset + BFI.StorageOffset.getQuantity(),
                  BFI.StorageSize / CharWidth, BFI.Offset,
                  BFI.Size, CharWidth,
                  CGM.getDataLayout().isBigEndian());
      continue;
    }

    setUsedBits(CGM, F->getType(),
                Offset + ASTLayout.getFieldOffset(Idx) / CharWidth, Bits);
  }
}

// Set the bits in `Bits`, which correspond to the value representations of
// the elements of an array type `ATy`.
static void setUsedBits(CodeGenModule &CGM, const ConstantArrayType *ATy,
                        int Offset, SmallVectorImpl<uint64_t> &Bits) {
  const ASTContext &Context = CGM.getContext();

  QualType ETy = Context.getBaseElementType(ATy);
  int Size = Context.getTypeSizeInChars(ETy).getQuantity();
  SmallVector<uint64_t, 4> TmpBits(Size);
  setUsedBits(CGM, ETy, 0, TmpBits);

  for (int I = 0, N = Context.getConstantArrayElementCount(ATy); I < N; ++I) {
    auto Src = TmpBits.begin();
    auto Dst = Bits.begin() + Offset + I * Size;
    for (int J = 0; J < Size; ++J)
      *Dst++ |= *Src++;
  }
}

// Set the bits in `Bits`, which correspond to the value representations of
// the type `QTy`.
static void setUsedBits(CodeGenModule &CGM, QualType QTy, int Offset,
                        SmallVectorImpl<uint64_t> &Bits) {
  if (const auto *RTy = QTy->getAs<RecordType>())
    return setUsedBits(CGM, RTy, Offset, Bits);

  ASTContext &Context = CGM.getContext();
  if (const auto *ATy = Context.getAsConstantArrayType(QTy))
    return setUsedBits(CGM, ATy, Offset, Bits);

  int Size = Context.getTypeSizeInChars(QTy).getQuantity();
  if (Size <= 0)
    return;

  std::fill_n(Bits.begin() + Offset, Size,
              (uint64_t(1) << Context.getCharWidth()) - 1);
}

static uint64_t buildMultiCharMask(const SmallVectorImpl<uint64_t> &Bits,
                                   int Pos, int Size, int CharWidth,
                                   bool BigEndian) {
  assert(Size > 0);
  uint64_t Mask = 0;
  if (BigEndian) {
    for (auto P = Bits.begin() + Pos, E = Bits.begin() + Pos + Size; P != E;
         ++P)
      Mask = (Mask << CharWidth) | *P;
  } else {
    auto P = Bits.begin() + Pos + Size, End = Bits.begin() + Pos;
    do
      Mask = (Mask << CharWidth) | *--P;
    while (P != End);
  }
  return Mask;
}

// Emit code to clear the bits in a record, which aren't a part of any user
// declared member, when the record is a function return.
llvm::Value *CodeGenFunction::EmitCMSEClearRecord(llvm::Value *Src,
                                                  llvm::IntegerType *ITy,
                                                  QualType QTy) {
  assert(Src->getType() == ITy);
  assert(ITy->getScalarSizeInBits() <= 64);

  const llvm::DataLayout &DataLayout = CGM.getDataLayout();
  int Size = DataLayout.getTypeStoreSize(ITy);
  SmallVector<uint64_t, 4> Bits(Size);
  setUsedBits(CGM, QTy->castAs<RecordType>(), 0, Bits);

  int CharWidth = CGM.getContext().getCharWidth();
  uint64_t Mask =
      buildMultiCharMask(Bits, 0, Size, CharWidth, DataLayout.isBigEndian());

  return Builder.CreateAnd(Src, Mask, "cmse.clear");
}

// Emit code to clear the bits in a record, which aren't a part of any user
// declared member, when the record is a function argument.
llvm::Value *CodeGenFunction::EmitCMSEClearRecord(llvm::Value *Src,
                                                  llvm::ArrayType *ATy,
                                                  QualType QTy) {
  const llvm::DataLayout &DataLayout = CGM.getDataLayout();
  int Size = DataLayout.getTypeStoreSize(ATy);
  SmallVector<uint64_t, 16> Bits(Size);
  setUsedBits(CGM, QTy->castAs<RecordType>(), 0, Bits);

  // Clear each element of the LLVM array.
  int CharWidth = CGM.getContext().getCharWidth();
  int CharsPerElt =
      ATy->getArrayElementType()->getScalarSizeInBits() / CharWidth;
  int MaskIndex = 0;
  llvm::Value *R = llvm::UndefValue::get(ATy);
  for (int I = 0, N = ATy->getArrayNumElements(); I != N; ++I) {
    uint64_t Mask = buildMultiCharMask(Bits, MaskIndex, CharsPerElt, CharWidth,
                                       DataLayout.isBigEndian());
    MaskIndex += CharsPerElt;
    llvm::Value *T0 = Builder.CreateExtractValue(Src, I);
    llvm::Value *T1 = Builder.CreateAnd(T0, Mask, "cmse.clear");
    R = Builder.CreateInsertValue(R, T1, I);
  }

  return R;
}

void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI,
                                         bool EmitRetDbgLoc,
                                         SourceLocation EndLoc) {
  if (FI.isNoReturn()) {
    // Noreturn functions don't return.
    EmitUnreachable(EndLoc);
    return;
  }

  if (CurCodeDecl && CurCodeDecl->hasAttr<NakedAttr>()) {
    // Naked functions don't have epilogues.
    Builder.CreateUnreachable();
    return;
  }

  // Functions with no result always return void.
  if (!ReturnValue.isValid()) {
    Builder.CreateRetVoid();
    return;
  }

  llvm::DebugLoc RetDbgLoc;
  llvm::Value *RV = nullptr;
  QualType RetTy = FI.getReturnType();
  const ABIArgInfo &RetAI = FI.getReturnInfo();

  switch (RetAI.getKind()) {
  case ABIArgInfo::InAlloca:
    // Aggregrates get evaluated directly into the destination.  Sometimes we
    // need to return the sret value in a register, though.
    assert(hasAggregateEvaluationKind(RetTy));
    if (RetAI.getInAllocaSRet()) {
      llvm::Function::arg_iterator EI = CurFn->arg_end();
      --EI;
      llvm::Value *ArgStruct = &*EI;
      llvm::Value *SRet = Builder.CreateStructGEP(
          nullptr, ArgStruct, RetAI.getInAllocaFieldIndex());
      RV = Builder.CreateAlignedLoad(SRet, getPointerAlign(), "sret");
    }
    break;

  case ABIArgInfo::Indirect: {
    auto AI = CurFn->arg_begin();
    if (RetAI.isSRetAfterThis())
      ++AI;
    switch (getEvaluationKind(RetTy)) {
    case TEK_Complex: {
      ComplexPairTy RT =
        EmitLoadOfComplex(MakeAddrLValue(ReturnValue, RetTy), EndLoc);
      EmitStoreOfComplex(RT, MakeNaturalAlignAddrLValue(&*AI, RetTy),
                         /*isInit*/ true);
      break;
    }
    case TEK_Aggregate:
      // Do nothing; aggregrates get evaluated directly into the destination.
      break;
    case TEK_Scalar:
      EmitStoreOfScalar(Builder.CreateLoad(ReturnValue),
                        MakeNaturalAlignAddrLValue(&*AI, RetTy),
                        /*isInit*/ true);
      break;
    }
    break;
  }

  case ABIArgInfo::Extend:
  case ABIArgInfo::Direct:
    if (RetAI.getCoerceToType() == ConvertType(RetTy) &&
        RetAI.getDirectOffset() == 0) {
      // The internal return value temp always will have pointer-to-return-type
      // type, just do a load.

      // If there is a dominating store to ReturnValue, we can elide
      // the load, zap the store, and usually zap the alloca.
      if (llvm::StoreInst *SI =
              findDominatingStoreToReturnValue(*this)) {
        // Reuse the debug location from the store unless there is
        // cleanup code to be emitted between the store and return
        // instruction.
        if (EmitRetDbgLoc && !AutoreleaseResult)
          RetDbgLoc = SI->getDebugLoc();
        // Get the stored value and nuke the now-dead store.
        RV = SI->getValueOperand();
        SI->eraseFromParent();

      // Otherwise, we have to do a simple load.
      } else {
        RV = Builder.CreateLoad(ReturnValue);
      }
    } else {
      // If the value is offset in memory, apply the offset now.
      Address V = emitAddressAtOffset(*this, ReturnValue, RetAI);

      RV = CreateCoercedLoad(V, RetAI.getCoerceToType(), *this);
    }

    // In ARC, end functions that return a retainable type with a call
    // to objc_autoreleaseReturnValue.
    if (AutoreleaseResult) {
#ifndef NDEBUG
      // Type::isObjCRetainabletype has to be called on a QualType that hasn't
      // been stripped of the typedefs, so we cannot use RetTy here. Get the
      // original return type of FunctionDecl, CurCodeDecl, and BlockDecl from
      // CurCodeDecl or BlockInfo.
      QualType RT;

      if (auto *FD = dyn_cast<FunctionDecl>(CurCodeDecl))
        RT = FD->getReturnType();
      else if (auto *MD = dyn_cast<ObjCMethodDecl>(CurCodeDecl))
        RT = MD->getReturnType();
      else if (isa<BlockDecl>(CurCodeDecl))
        RT = BlockInfo->BlockExpression->getFunctionType()->getReturnType();
      else
        llvm_unreachable("Unexpected function/method type");

      assert(getLangOpts().ObjCAutoRefCount &&
             !FI.isReturnsRetained() &&
             RT->isObjCRetainableType());
#endif
      RV = emitAutoreleaseOfResult(*this, RV);
    }

    break;

  case ABIArgInfo::Ignore:
    break;

  case ABIArgInfo::CoerceAndExpand: {
    auto coercionType = RetAI.getCoerceAndExpandType();

    // Load all of the coerced elements out into results.
    llvm::SmallVector<llvm::Value*, 4> results;
    Address addr = Builder.CreateElementBitCast(ReturnValue, coercionType);
    for (unsigned i = 0, e = coercionType->getNumElements(); i != e; ++i) {
      auto coercedEltType = coercionType->getElementType(i);
      if (ABIArgInfo::isPaddingForCoerceAndExpand(coercedEltType))
        continue;

      auto eltAddr = Builder.CreateStructGEP(addr, i);
      auto elt = Builder.CreateLoad(eltAddr);
      results.push_back(elt);
    }

    // If we have one result, it's the single direct result type.
    if (results.size() == 1) {
      RV = results[0];

    // Otherwise, we need to make a first-class aggregate.
    } else {
      // Construct a return type that lacks padding elements.
      llvm::Type *returnType = RetAI.getUnpaddedCoerceAndExpandType();

      RV = llvm::UndefValue::get(returnType);
      for (unsigned i = 0, e = results.size(); i != e; ++i) {
        RV = Builder.CreateInsertValue(RV, results[i], i);
      }
    }
    break;
  }
  case ABIArgInfo::Expand:
  case ABIArgInfo::IndirectAliased:
    llvm_unreachable("Invalid ABI kind for return argument");
  }

  llvm::Instruction *Ret;
  if (RV) {
    if (CurFuncDecl && CurFuncDecl->hasAttr<CmseNSEntryAttr>()) {
      // For certain return types, clear padding bits, as they may reveal
      // sensitive information.
      // Small struct/union types are passed as integers.
      auto *ITy = dyn_cast<llvm::IntegerType>(RV->getType());
      if (ITy != nullptr && isa<RecordType>(RetTy.getCanonicalType()))
        RV = EmitCMSEClearRecord(RV, ITy, RetTy);
    }
    EmitReturnValueCheck(RV);
    Ret = Builder.CreateRet(RV);
  } else {
    Ret = Builder.CreateRetVoid();
  }

  if (RetDbgLoc)
    Ret->setDebugLoc(std::move(RetDbgLoc));
}

void CodeGenFunction::EmitReturnValueCheck(llvm::Value *RV) {
  // A current decl may not be available when emitting vtable thunks.
  if (!CurCodeDecl)
    return;

  // If the return block isn't reachable, neither is this check, so don't emit
  // it.
  if (ReturnBlock.isValid() && ReturnBlock.getBlock()->use_empty())
    return;

  ReturnsNonNullAttr *RetNNAttr = nullptr;
  if (SanOpts.has(SanitizerKind::ReturnsNonnullAttribute))
    RetNNAttr = CurCodeDecl->getAttr<ReturnsNonNullAttr>();

  if (!RetNNAttr && !requiresReturnValueNullabilityCheck())
    return;

  // Prefer the returns_nonnull attribute if it's present.
  SourceLocation AttrLoc;
  SanitizerMask CheckKind;
  SanitizerHandler Handler;
  if (RetNNAttr) {
    assert(!requiresReturnValueNullabilityCheck() &&
           "Cannot check nullability and the nonnull attribute");
    AttrLoc = RetNNAttr->getLocation();
    CheckKind = SanitizerKind::ReturnsNonnullAttribute;
    Handler = SanitizerHandler::NonnullReturn;
  } else {
    if (auto *DD = dyn_cast<DeclaratorDecl>(CurCodeDecl))
      if (auto *TSI = DD->getTypeSourceInfo())
        if (auto FTL = TSI->getTypeLoc().getAsAdjusted<FunctionTypeLoc>())
          AttrLoc = FTL.getReturnLoc().findNullabilityLoc();
    CheckKind = SanitizerKind::NullabilityReturn;
    Handler = SanitizerHandler::NullabilityReturn;
  }

  SanitizerScope SanScope(this);

  // Make sure the "return" source location is valid. If we're checking a
  // nullability annotation, make sure the preconditions for the check are met.
  llvm::BasicBlock *Check = createBasicBlock("nullcheck");
  llvm::BasicBlock *NoCheck = createBasicBlock("no.nullcheck");
  llvm::Value *SLocPtr = Builder.CreateLoad(ReturnLocation, "return.sloc.load");
  llvm::Value *CanNullCheck = Builder.CreateIsNotNull(SLocPtr);
  if (requiresReturnValueNullabilityCheck())
    CanNullCheck =
        Builder.CreateAnd(CanNullCheck, RetValNullabilityPrecondition);
  Builder.CreateCondBr(CanNullCheck, Check, NoCheck);
  EmitBlock(Check);

  // Now do the null check.
  llvm::Value *Cond = Builder.CreateIsNotNull(RV);
  llvm::Constant *StaticData[] = {EmitCheckSourceLocation(AttrLoc)};
  llvm::Value *DynamicData[] = {SLocPtr};
  EmitCheck(std::make_pair(Cond, CheckKind), Handler, StaticData, DynamicData);

  EmitBlock(NoCheck);

#ifndef NDEBUG
  // The return location should not be used after the check has been emitted.
  ReturnLocation = Address::invalid();
#endif
}

static bool isInAllocaArgument(CGCXXABI &ABI, QualType type) {
  const CXXRecordDecl *RD = type->getAsCXXRecordDecl();
  return RD && ABI.getRecordArgABI(RD) == CGCXXABI::RAA_DirectInMemory;
}

static AggValueSlot createPlaceholderSlot(CodeGenFunction &CGF,
                                          QualType Ty) {
  // FIXME: Generate IR in one pass, rather than going back and fixing up these
  // placeholders.
  llvm::Type *IRTy = CGF.ConvertTypeForMem(Ty);
  llvm::Type *IRPtrTy = IRTy->getPointerTo();
  llvm::Value *Placeholder = llvm::UndefValue::get(IRPtrTy->getPointerTo());

  // FIXME: When we generate this IR in one pass, we shouldn't need
  // this win32-specific alignment hack.
  CharUnits Align = CharUnits::fromQuantity(4);
  Placeholder = CGF.Builder.CreateAlignedLoad(IRPtrTy, Placeholder, Align);

  return AggValueSlot::forAddr(Address(Placeholder, Align),
                               Ty.getQualifiers(),
                               AggValueSlot::IsNotDestructed,
                               AggValueSlot::DoesNotNeedGCBarriers,
                               AggValueSlot::IsNotAliased,
                               AggValueSlot::DoesNotOverlap);
}

void CodeGenFunction::EmitDelegateCallArg(CallArgList &args,
                                          const VarDecl *param,
                                          SourceLocation loc) {
  // StartFunction converted the ABI-lowered parameter(s) into a
  // local alloca.  We need to turn that into an r-value suitable
  // for EmitCall.
  Address local = GetAddrOfLocalVar(param);

  QualType type = param->getType();

  if (isInAllocaArgument(CGM.getCXXABI(), type)) {
    CGM.ErrorUnsupported(param, "forwarded non-trivially copyable parameter");
  }

  // GetAddrOfLocalVar returns a pointer-to-pointer for references,
  // but the argument needs to be the original pointer.
  if (type->isReferenceType()) {
    args.add(RValue::get(Builder.CreateLoad(local)), type);

  // In ARC, move out of consumed arguments so that the release cleanup
  // entered by StartFunction doesn't cause an over-release.  This isn't
  // optimal -O0 code generation, but it should get cleaned up when
  // optimization is enabled.  This also assumes that delegate calls are
  // performed exactly once for a set of arguments, but that should be safe.
  } else if (getLangOpts().ObjCAutoRefCount &&
             param->hasAttr<NSConsumedAttr>() &&
             type->isObjCRetainableType()) {
    llvm::Value *ptr = Builder.CreateLoad(local);
    auto null =
      llvm::ConstantPointerNull::get(cast<llvm::PointerType>(ptr->getType()));
    Builder.CreateStore(null, local);
    args.add(RValue::get(ptr), type);

  // For the most part, we just need to load the alloca, except that
  // aggregate r-values are actually pointers to temporaries.
  } else {
    args.add(convertTempToRValue(local, type, loc), type);
  }

  // Deactivate the cleanup for the callee-destructed param that was pushed.
  if (hasAggregateEvaluationKind(type) && !CurFuncIsThunk &&
      type->castAs<RecordType>()->getDecl()->isParamDestroyedInCallee() &&
      param->needsDestruction(getContext())) {
    EHScopeStack::stable_iterator cleanup =
        CalleeDestructedParamCleanups.lookup(cast<ParmVarDecl>(param));
    assert(cleanup.isValid() &&
           "cleanup for callee-destructed param not recorded");
    // This unreachable is a temporary marker which will be removed later.
    llvm::Instruction *isActive = Builder.CreateUnreachable();
    args.addArgCleanupDeactivation(cleanup, isActive);
  }
}

static bool isProvablyNull(llvm::Value *addr) {
  return isa<llvm::ConstantPointerNull>(addr);
}

/// Emit the actual writing-back of a writeback.
static void emitWriteback(CodeGenFunction &CGF,
                          const CallArgList::Writeback &writeback) {
  const LValue &srcLV = writeback.Source;
  Address srcAddr = srcLV.getAddress(CGF);
  assert(!isProvablyNull(srcAddr.getPointer()) &&
         "shouldn't have writeback for provably null argument");

  llvm::BasicBlock *contBB = nullptr;

  // If the argument wasn't provably non-null, we need to null check
  // before doing the store.
  bool provablyNonNull = llvm::isKnownNonZero(srcAddr.getPointer(),
                                              CGF.CGM.getDataLayout());
  if (!provablyNonNull) {
    llvm::BasicBlock *writebackBB = CGF.createBasicBlock("icr.writeback");
    contBB = CGF.createBasicBlock("icr.done");

    llvm::Value *isNull =
      CGF.Builder.CreateIsNull(srcAddr.getPointer(), "icr.isnull");
    CGF.Builder.CreateCondBr(isNull, contBB, writebackBB);
    CGF.EmitBlock(writebackBB);
  }

  // Load the value to writeback.
  llvm::Value *value = CGF.Builder.CreateLoad(writeback.Temporary);

  // Cast it back, in case we're writing an id to a Foo* or something.
  value = CGF.Builder.CreateBitCast(value, srcAddr.getElementType(),
                                    "icr.writeback-cast");

  // Perform the writeback.

  // If we have a "to use" value, it's something we need to emit a use
  // of.  This has to be carefully threaded in: if it's done after the
  // release it's potentially undefined behavior (and the optimizer
  // will ignore it), and if it happens before the retain then the
  // optimizer could move the release there.
  if (writeback.ToUse) {
    assert(srcLV.getObjCLifetime() == Qualifiers::OCL_Strong);

    // Retain the new value.  No need to block-copy here:  the block's
    // being passed up the stack.
    value = CGF.EmitARCRetainNonBlock(value);

    // Emit the intrinsic use here.
    CGF.EmitARCIntrinsicUse(writeback.ToUse);

    // Load the old value (primitively).
    llvm::Value *oldValue = CGF.EmitLoadOfScalar(srcLV, SourceLocation());