lib/CodeGen/CGAtomic.cpp

//===--- CGAtomic.cpp - Emit LLVM IR for atomic operations ----------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the code for emitting atomic operations.
//
//===----------------------------------------------------------------------===//

#include "CodeGenFunction.h"
#include "CGCall.h"
#include "CGRecordLayout.h"
#include "CodeGenModule.h"
#include "clang/AST/ASTContext.h"
#include "clang/CodeGen/CGFunctionInfo.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Operator.h"

using namespace clang;
using namespace CodeGen;

namespace {
  class AtomicInfo {
    CodeGenFunction &CGF;
    QualType AtomicTy;
    QualType ValueTy;
    uint64_t AtomicSizeInBits;
    uint64_t ValueSizeInBits;
    CharUnits AtomicAlign;
    CharUnits ValueAlign;
    CharUnits LValueAlign;
    TypeEvaluationKind EvaluationKind;
    bool UseLibcall;
    LValue LVal;
    CGBitFieldInfo BFI;
  public:
    AtomicInfo(CodeGenFunction &CGF, LValue &lvalue)
        : CGF(CGF), AtomicSizeInBits(0), ValueSizeInBits(0),
          EvaluationKind(TEK_Scalar), UseLibcall(true) {
      assert(!lvalue.isGlobalReg());
      ASTContext &C = CGF.getContext();
      if (lvalue.isSimple()) {
        AtomicTy = lvalue.getType();
        if (auto *ATy = AtomicTy->getAs<AtomicType>())
          ValueTy = ATy->getValueType();
        else
          ValueTy = AtomicTy;
        EvaluationKind = CGF.getEvaluationKind(ValueTy);

        uint64_t ValueAlignInBits;
        uint64_t AtomicAlignInBits;
        TypeInfo ValueTI = C.getTypeInfo(ValueTy);
        ValueSizeInBits = ValueTI.Width;
        ValueAlignInBits = ValueTI.Align;

        TypeInfo AtomicTI = C.getTypeInfo(AtomicTy);
        AtomicSizeInBits = AtomicTI.Width;
        AtomicAlignInBits = AtomicTI.Align;

        assert(ValueSizeInBits <= AtomicSizeInBits);
        assert(ValueAlignInBits <= AtomicAlignInBits);

        AtomicAlign = C.toCharUnitsFromBits(AtomicAlignInBits);
        ValueAlign = C.toCharUnitsFromBits(ValueAlignInBits);
        if (lvalue.getAlignment().isZero())
          lvalue.setAlignment(AtomicAlign);

        LVal = lvalue;
      } else if (lvalue.isBitField()) {
        auto &OrigBFI = lvalue.getBitFieldInfo();
        auto Offset = OrigBFI.Offset % C.toBits(lvalue.getAlignment());
        AtomicSizeInBits = C.toBits(
            C.toCharUnitsFromBits(Offset + OrigBFI.Size + C.getCharWidth() - 1)
                .RoundUpToAlignment(lvalue.getAlignment()));
        auto VoidPtrAddr = CGF.EmitCastToVoidPtr(lvalue.getBitFieldAddr());
        auto OffsetInChars =
            (C.toCharUnitsFromBits(OrigBFI.Offset) / lvalue.getAlignment()) *
            lvalue.getAlignment();
        VoidPtrAddr = CGF.Builder.CreateConstGEP1_64(
            VoidPtrAddr, OffsetInChars.getQuantity());
        auto Addr = CGF.Builder.CreatePointerBitCastOrAddrSpaceCast(
            VoidPtrAddr,
            CGF.Builder.getIntNTy(AtomicSizeInBits)->getPointerTo(),
            "atomic_bitfield_base");
        BFI = OrigBFI;
        BFI.Offset = Offset;
        BFI.StorageSize = AtomicSizeInBits;
        LVal = LValue::MakeBitfield(Addr, BFI, lvalue.getType(),
                                    lvalue.getAlignment());
      } else if (lvalue.isVectorElt()) {
        AtomicSizeInBits = C.getTypeSize(lvalue.getType());
        LVal = lvalue;
      } else {
        assert(lvalue.isExtVectorElt());
        AtomicSizeInBits = C.getTypeSize(lvalue.getType());
        LVal = lvalue;
      }
      UseLibcall = !C.getTargetInfo().hasBuiltinAtomic(
          AtomicSizeInBits, C.toBits(lvalue.getAlignment()));
    }

    QualType getAtomicType() const { return AtomicTy; }
    QualType getValueType() const { return ValueTy; }
    CharUnits getAtomicAlignment() const { return AtomicAlign; }
    CharUnits getValueAlignment() const { return ValueAlign; }
    uint64_t getAtomicSizeInBits() const { return AtomicSizeInBits; }
    uint64_t getValueSizeInBits() const { return ValueSizeInBits; }
    TypeEvaluationKind getEvaluationKind() const { return EvaluationKind; }
    bool shouldUseLibcall() const { return UseLibcall; }
    const LValue &getAtomicLValue() const { return LVal; }

    /// Is the atomic size larger than the underlying value type?
    ///
    /// Note that the absence of padding does not mean that atomic
    /// objects are completely interchangeable with non-atomic
    /// objects: we might have promoted the alignment of a type
    /// without making it bigger.
    bool hasPadding() const {
      return (ValueSizeInBits != AtomicSizeInBits);
    }

    bool emitMemSetZeroIfNecessary() const;

    llvm::Value *getAtomicSizeValue() const {
      CharUnits size = CGF.getContext().toCharUnitsFromBits(AtomicSizeInBits);
      return CGF.CGM.getSize(size);
    }

    /// Cast the given pointer to an integer pointer suitable for
    /// atomic operations.
    llvm::Value *emitCastToAtomicIntPointer(llvm::Value *addr) const;

    /// Turn an atomic-layout object into an r-value.
    RValue convertTempToRValue(llvm::Value *addr,
                               AggValueSlot resultSlot,
                               SourceLocation loc) const;

    /// \brief Converts a rvalue to integer value.
    llvm::Value *convertRValueToInt(RValue RVal) const;

    RValue convertIntToValue(llvm::Value *IntVal, AggValueSlot ResultSlot,
                             SourceLocation Loc) const;

    /// Copy an atomic r-value into atomic-layout memory.
    void emitCopyIntoMemory(RValue rvalue) const;

    /// Project an l-value down to the value field.
    LValue projectValue() const {
      assert(LVal.isSimple());
      llvm::Value *addr = LVal.getAddress();
      if (hasPadding())
        addr = CGF.Builder.CreateStructGEP(addr, 0);

      return LValue::MakeAddr(addr, getValueType(), LVal.getAlignment(),
                              CGF.getContext(), LVal.getTBAAInfo());
    }

    /// Materialize an atomic r-value in atomic-layout memory.
    llvm::Value *materializeRValue(RValue rvalue) const;

  private:
    bool requiresMemSetZero(llvm::Type *type) const;
  };
}

static RValue emitAtomicLibcall(CodeGenFunction &CGF,
                                StringRef fnName,
                                QualType resultType,
                                CallArgList &args) {
  const CGFunctionInfo &fnInfo =
    CGF.CGM.getTypes().arrangeFreeFunctionCall(resultType, args,
            FunctionType::ExtInfo(), RequiredArgs::All);
  llvm::FunctionType *fnTy = CGF.CGM.getTypes().GetFunctionType(fnInfo);
  llvm::Constant *fn = CGF.CGM.CreateRuntimeFunction(fnTy, fnName);
  return CGF.EmitCall(fnInfo, fn, ReturnValueSlot(), args);
}

/// Does a store of the given IR type modify the full expected width?
static bool isFullSizeType(CodeGenModule &CGM, llvm::Type *type,
                           uint64_t expectedSize) {
  return (CGM.getDataLayout().getTypeStoreSize(type) * 8 == expectedSize);
}

/// Does the atomic type require memsetting to zero before initialization?
///
/// The IR type is provided as a way of making certain queries faster.
bool AtomicInfo::requiresMemSetZero(llvm::Type *type) const {
  // If the atomic type has size padding, we definitely need a memset.
  if (hasPadding()) return true;

  // Otherwise, do some simple heuristics to try to avoid it:
  switch (getEvaluationKind()) {
  // For scalars and complexes, check whether the store size of the
  // type uses the full size.
  case TEK_Scalar:
    return !isFullSizeType(CGF.CGM, type, AtomicSizeInBits);
  case TEK_Complex:
    return !isFullSizeType(CGF.CGM, type->getStructElementType(0),
                           AtomicSizeInBits / 2);

  // Padding in structs has an undefined bit pattern.  User beware.
  case TEK_Aggregate:
    return false;
  }
  llvm_unreachable("bad evaluation kind");
}

bool AtomicInfo::emitMemSetZeroIfNecessary() const {
  assert(LVal.isSimple());
  llvm::Value *addr = LVal.getAddress();
  if (!requiresMemSetZero(addr->getType()->getPointerElementType()))
    return false;

  CGF.Builder.CreateMemSet(addr, llvm::ConstantInt::get(CGF.Int8Ty, 0),
                           AtomicSizeInBits / 8,
                           LVal.getAlignment().getQuantity());
  return true;
}

static void emitAtomicCmpXchg(CodeGenFunction &CGF, AtomicExpr *E, bool IsWeak,
                              llvm::Value *Dest, llvm::Value *Ptr,
                              llvm::Value *Val1, llvm::Value *Val2,
                              uint64_t Size, unsigned Align,
                              llvm::AtomicOrdering SuccessOrder,
                              llvm::AtomicOrdering FailureOrder) {
  // Note that cmpxchg doesn't support weak cmpxchg, at least at the moment.
  llvm::LoadInst *Expected = CGF.Builder.CreateLoad(Val1);
  Expected->setAlignment(Align);
  llvm::LoadInst *Desired = CGF.Builder.CreateLoad(Val2);
  Desired->setAlignment(Align);

  llvm::AtomicCmpXchgInst *Pair = CGF.Builder.CreateAtomicCmpXchg(
      Ptr, Expected, Desired, SuccessOrder, FailureOrder);
  Pair->setVolatile(E->isVolatile());
  Pair->setWeak(IsWeak);

  // Cmp holds the result of the compare-exchange operation: true on success,
  // false on failure.
  llvm::Value *Old = CGF.Builder.CreateExtractValue(Pair, 0);
  llvm::Value *Cmp = CGF.Builder.CreateExtractValue(Pair, 1);

  // This basic block is used to hold the store instruction if the operation
  // failed.
  llvm::BasicBlock *StoreExpectedBB =
      CGF.createBasicBlock("cmpxchg.store_expected", CGF.CurFn);

  // This basic block is the exit point of the operation, we should end up
  // here regardless of whether or not the operation succeeded.
  llvm::BasicBlock *ContinueBB =
      CGF.createBasicBlock("cmpxchg.continue", CGF.CurFn);

  // Update Expected if Expected isn't equal to Old, otherwise branch to the
  // exit point.
  CGF.Builder.CreateCondBr(Cmp, ContinueBB, StoreExpectedBB);

  CGF.Builder.SetInsertPoint(StoreExpectedBB);
  // Update the memory at Expected with Old's value.
  llvm::StoreInst *StoreExpected = CGF.Builder.CreateStore(Old, Val1);
  StoreExpected->setAlignment(Align);
  // Finally, branch to the exit point.
  CGF.Builder.CreateBr(ContinueBB);

  CGF.Builder.SetInsertPoint(ContinueBB);
  // Update the memory at Dest with Cmp's value.
  CGF.EmitStoreOfScalar(Cmp, CGF.MakeAddrLValue(Dest, E->getType()));
  return;
}

/// Given an ordering required on success, emit all possible cmpxchg
/// instructions to cope with the provided (but possibly only dynamically known)
/// FailureOrder.
static void emitAtomicCmpXchgFailureSet(CodeGenFunction &CGF, AtomicExpr *E,
                                        bool IsWeak, llvm::Value *Dest,
                                        llvm::Value *Ptr, llvm::Value *Val1,
                                        llvm::Value *Val2,
                                        llvm::Value *FailureOrderVal,
                                        uint64_t Size, unsigned Align,
                                        llvm::AtomicOrdering SuccessOrder) {
  llvm::AtomicOrdering FailureOrder;
  if (llvm::ConstantInt *FO = dyn_cast<llvm::ConstantInt>(FailureOrderVal)) {
    switch (FO->getSExtValue()) {
    default:
      FailureOrder = llvm::Monotonic;
      break;
    case AtomicExpr::AO_ABI_memory_order_consume:
    case AtomicExpr::AO_ABI_memory_order_acquire:
      FailureOrder = llvm::Acquire;
      break;
    case AtomicExpr::AO_ABI_memory_order_seq_cst:
      FailureOrder = llvm::SequentiallyConsistent;
      break;
    }
    if (FailureOrder >= SuccessOrder) {
      // Don't assert on undefined behaviour.
      FailureOrder =
        llvm::AtomicCmpXchgInst::getStrongestFailureOrdering(SuccessOrder);
    }
    emitAtomicCmpXchg(CGF, E, IsWeak, Dest, Ptr, Val1, Val2, Size, Align,
                      SuccessOrder, FailureOrder);
    return;
  }

  // Create all the relevant BB's
  llvm::BasicBlock *MonotonicBB = nullptr, *AcquireBB = nullptr,
                   *SeqCstBB = nullptr;
  MonotonicBB = CGF.createBasicBlock("monotonic_fail", CGF.CurFn);
  if (SuccessOrder != llvm::Monotonic && SuccessOrder != llvm::Release)
    AcquireBB = CGF.createBasicBlock("acquire_fail", CGF.CurFn);
  if (SuccessOrder == llvm::SequentiallyConsistent)
    SeqCstBB = CGF.createBasicBlock("seqcst_fail", CGF.CurFn);

  llvm::BasicBlock *ContBB = CGF.createBasicBlock("atomic.continue", CGF.CurFn);

  llvm::SwitchInst *SI = CGF.Builder.CreateSwitch(FailureOrderVal, MonotonicBB);

  // Emit all the different atomics

  // MonotonicBB is arbitrarily chosen as the default case; in practice, this
  // doesn't matter unless someone is crazy enough to use something that
  // doesn't fold to a constant for the ordering.
  CGF.Builder.SetInsertPoint(MonotonicBB);
  emitAtomicCmpXchg(CGF, E, IsWeak, Dest, Ptr, Val1, Val2,
                    Size, Align, SuccessOrder, llvm::Monotonic);
  CGF.Builder.CreateBr(ContBB);

  if (AcquireBB) {
    CGF.Builder.SetInsertPoint(AcquireBB);
    emitAtomicCmpXchg(CGF, E, IsWeak, Dest, Ptr, Val1, Val2,
                      Size, Align, SuccessOrder, llvm::Acquire);
    CGF.Builder.CreateBr(ContBB);
    SI->addCase(CGF.Builder.getInt32(AtomicExpr::AO_ABI_memory_order_consume),
                AcquireBB);
    SI->addCase(CGF.Builder.getInt32(AtomicExpr::AO_ABI_memory_order_acquire),
                AcquireBB);
  }
  if (SeqCstBB) {
    CGF.Builder.SetInsertPoint(SeqCstBB);
    emitAtomicCmpXchg(CGF, E, IsWeak, Dest, Ptr, Val1, Val2,
                      Size, Align, SuccessOrder, llvm::SequentiallyConsistent);
    CGF.Builder.CreateBr(ContBB);
    SI->addCase(CGF.Builder.getInt32(AtomicExpr::AO_ABI_memory_order_seq_cst),
                SeqCstBB);
  }

  CGF.Builder.SetInsertPoint(ContBB);
}

static void EmitAtomicOp(CodeGenFunction &CGF, AtomicExpr *E, llvm::Value *Dest,
                         llvm::Value *Ptr, llvm::Value *Val1, llvm::Value *Val2,
                         llvm::Value *IsWeak, llvm::Value *FailureOrder,
                         uint64_t Size, unsigned Align,
                         llvm::AtomicOrdering Order) {
  llvm::AtomicRMWInst::BinOp Op = llvm::AtomicRMWInst::Add;
  llvm::Instruction::BinaryOps PostOp = (llvm::Instruction::BinaryOps)0;

  switch (E->getOp()) {
  case AtomicExpr::AO__c11_atomic_init:
    llvm_unreachable("Already handled!");

  case AtomicExpr::AO__c11_atomic_compare_exchange_strong:
    emitAtomicCmpXchgFailureSet(CGF, E, false, Dest, Ptr, Val1, Val2,
                                FailureOrder, Size, Align, Order);
    return;
  case AtomicExpr::AO__c11_atomic_compare_exchange_weak:
    emitAtomicCmpXchgFailureSet(CGF, E, true, Dest, Ptr, Val1, Val2,
                                FailureOrder, Size, Align, Order);
    return;
  case AtomicExpr::AO__atomic_compare_exchange:
  case AtomicExpr::AO__atomic_compare_exchange_n: {
    if (llvm::ConstantInt *IsWeakC = dyn_cast<llvm::ConstantInt>(IsWeak)) {
      emitAtomicCmpXchgFailureSet(CGF, E, IsWeakC->getZExtValue(), Dest, Ptr,
                                  Val1, Val2, FailureOrder, Size, Align, Order);
    } else {
      // Create all the relevant BB's
      llvm::BasicBlock *StrongBB =
          CGF.createBasicBlock("cmpxchg.strong", CGF.CurFn);
      llvm::BasicBlock *WeakBB = CGF.createBasicBlock("cmxchg.weak", CGF.CurFn);
      llvm::BasicBlock *ContBB =
          CGF.createBasicBlock("cmpxchg.continue", CGF.CurFn);

      llvm::SwitchInst *SI = CGF.Builder.CreateSwitch(IsWeak, WeakBB);
      SI->addCase(CGF.Builder.getInt1(false), StrongBB);

      CGF.Builder.SetInsertPoint(StrongBB);
      emitAtomicCmpXchgFailureSet(CGF, E, false, Dest, Ptr, Val1, Val2,
                                  FailureOrder, Size, Align, Order);
      CGF.Builder.CreateBr(ContBB);

      CGF.Builder.SetInsertPoint(WeakBB);
      emitAtomicCmpXchgFailureSet(CGF, E, true, Dest, Ptr, Val1, Val2,
                                  FailureOrder, Size, Align, Order);
      CGF.Builder.CreateBr(ContBB);

      CGF.Builder.SetInsertPoint(ContBB);
    }
    return;
  }
  case AtomicExpr::AO__c11_atomic_load:
  case AtomicExpr::AO__atomic_load_n:
  case AtomicExpr::AO__atomic_load: {
    llvm::LoadInst *Load = CGF.Builder.CreateLoad(Ptr);
    Load->setAtomic(Order);
    Load->setAlignment(Size);
    Load->setVolatile(E->isVolatile());
    llvm::StoreInst *StoreDest = CGF.Builder.CreateStore(Load, Dest);
    StoreDest->setAlignment(Align);
    return;
  }

  case AtomicExpr::AO__c11_atomic_store:
  case AtomicExpr::AO__atomic_store:
  case AtomicExpr::AO__atomic_store_n: {
    assert(!Dest && "Store does not return a value");
    llvm::LoadInst *LoadVal1 = CGF.Builder.CreateLoad(Val1);
    LoadVal1->setAlignment(Align);
    llvm::StoreInst *Store = CGF.Builder.CreateStore(LoadVal1, Ptr);
    Store->setAtomic(Order);
    Store->setAlignment(Size);
    Store->setVolatile(E->isVolatile());
    return;
  }

  case AtomicExpr::AO__c11_atomic_exchange:
  case AtomicExpr::AO__atomic_exchange_n:
  case AtomicExpr::AO__atomic_exchange:
    Op = llvm::AtomicRMWInst::Xchg;
    break;

  case AtomicExpr::AO__atomic_add_fetch:
    PostOp = llvm::Instruction::Add;
    // Fall through.
  case AtomicExpr::AO__c11_atomic_fetch_add:
  case AtomicExpr::AO__atomic_fetch_add:
    Op = llvm::AtomicRMWInst::Add;
    break;

  case AtomicExpr::AO__atomic_sub_fetch:
    PostOp = llvm::Instruction::Sub;
    // Fall through.
  case AtomicExpr::AO__c11_atomic_fetch_sub:
  case AtomicExpr::AO__atomic_fetch_sub:
    Op = llvm::AtomicRMWInst::Sub;
    break;

  case AtomicExpr::AO__atomic_and_fetch:
    PostOp = llvm::Instruction::And;
    // Fall through.
  case AtomicExpr::AO__c11_atomic_fetch_and:
  case AtomicExpr::AO__atomic_fetch_and:
    Op = llvm::AtomicRMWInst::And;
    break;

  case AtomicExpr::AO__atomic_or_fetch:
    PostOp = llvm::Instruction::Or;
    // Fall through.
  case AtomicExpr::AO__c11_atomic_fetch_or:
  case AtomicExpr::AO__atomic_fetch_or:
    Op = llvm::AtomicRMWInst::Or;
    break;

  case AtomicExpr::AO__atomic_xor_fetch:
    PostOp = llvm::Instruction::Xor;
    // Fall through.
  case AtomicExpr::AO__c11_atomic_fetch_xor:
  case AtomicExpr::AO__atomic_fetch_xor:
    Op = llvm::AtomicRMWInst::Xor;
    break;

  case AtomicExpr::AO__atomic_nand_fetch:
    PostOp = llvm::Instruction::And;
    // Fall through.
  case AtomicExpr::AO__atomic_fetch_nand:
    Op = llvm::AtomicRMWInst::Nand;
    break;
  }

  llvm::LoadInst *LoadVal1 = CGF.Builder.CreateLoad(Val1);
  LoadVal1->setAlignment(Align);
  llvm::AtomicRMWInst *RMWI =
      CGF.Builder.CreateAtomicRMW(Op, Ptr, LoadVal1, Order);
  RMWI->setVolatile(E->isVolatile());

  // For __atomic_*_fetch operations, perform the operation again to
  // determine the value which was written.
  llvm::Value *Result = RMWI;
  if (PostOp)
    Result = CGF.Builder.CreateBinOp(PostOp, RMWI, LoadVal1);
  if (E->getOp() == AtomicExpr::AO__atomic_nand_fetch)
    Result = CGF.Builder.CreateNot(Result);
  llvm::StoreInst *StoreDest = CGF.Builder.CreateStore(Result, Dest);
  StoreDest->setAlignment(Align);
}

// This function emits any expression (scalar, complex, or aggregate)
// into a temporary alloca.
static llvm::Value *
EmitValToTemp(CodeGenFunction &CGF, Expr *E) {
  llvm::Value *DeclPtr = CGF.CreateMemTemp(E->getType(), ".atomictmp");
  CGF.EmitAnyExprToMem(E, DeclPtr, E->getType().getQualifiers(),
                       /*Init*/ true);
  return DeclPtr;
}

static void
AddDirectArgument(CodeGenFunction &CGF, CallArgList &Args,
                  bool UseOptimizedLibcall, llvm::Value *Val, QualType ValTy,
                  SourceLocation Loc, CharUnits SizeInChars) {
  if (UseOptimizedLibcall) {
    // Load value and pass it to the function directly.
    unsigned Align = CGF.getContext().getTypeAlignInChars(ValTy).getQuantity();
    int64_t SizeInBits = CGF.getContext().toBits(SizeInChars);
    ValTy =
        CGF.getContext().getIntTypeForBitwidth(SizeInBits, /*Signed=*/false);
    llvm::Type *IPtrTy = llvm::IntegerType::get(CGF.getLLVMContext(),
                                                SizeInBits)->getPointerTo();
    Val = CGF.EmitLoadOfScalar(CGF.Builder.CreateBitCast(Val, IPtrTy), false,
                               Align, CGF.getContext().getPointerType(ValTy),
                               Loc);
    // Coerce the value into an appropriately sized integer type.
    Args.add(RValue::get(Val), ValTy);
  } else {
    // Non-optimized functions always take a reference.
    Args.add(RValue::get(CGF.EmitCastToVoidPtr(Val)),
                         CGF.getContext().VoidPtrTy);
  }
}

RValue CodeGenFunction::EmitAtomicExpr(AtomicExpr *E, llvm::Value *Dest) {
  QualType AtomicTy = E->getPtr()->getType()->getPointeeType();
  QualType MemTy = AtomicTy;
  if (const AtomicType *AT = AtomicTy->getAs<AtomicType>())
    MemTy = AT->getValueType();
  CharUnits sizeChars = getContext().getTypeSizeInChars(AtomicTy);
  uint64_t Size = sizeChars.getQuantity();
  CharUnits alignChars = getContext().getTypeAlignInChars(AtomicTy);
  unsigned Align = alignChars.getQuantity();
  unsigned MaxInlineWidthInBits =
    getTarget().getMaxAtomicInlineWidth();
  bool UseLibcall = (Size != Align ||
                     getContext().toBits(sizeChars) > MaxInlineWidthInBits);

  llvm::Value *IsWeak = nullptr, *OrderFail = nullptr, *Val1 = nullptr,
              *Val2 = nullptr;
  llvm::Value *Ptr = EmitScalarExpr(E->getPtr());

  if (E->getOp() == AtomicExpr::AO__c11_atomic_init) {
    assert(!Dest && "Init does not return a value");
    LValue lvalue = LValue::MakeAddr(Ptr, AtomicTy, alignChars, getContext());
    EmitAtomicInit(E->getVal1(), lvalue);
    return RValue::get(nullptr);
  }

  llvm::Value *Order = EmitScalarExpr(E->getOrder());

  switch (E->getOp()) {
  case AtomicExpr::AO__c11_atomic_init:
    llvm_unreachable("Already handled!");

  case AtomicExpr::AO__c11_atomic_load:
  case AtomicExpr::AO__atomic_load_n:
    break;

  case AtomicExpr::AO__atomic_load:
    Dest = EmitScalarExpr(E->getVal1());
    break;

  case AtomicExpr::AO__atomic_store:
    Val1 = EmitScalarExpr(E->getVal1());
    break;

  case AtomicExpr::AO__atomic_exchange:
    Val1 = EmitScalarExpr(E->getVal1());
    Dest = EmitScalarExpr(E->getVal2());
    break;

  case AtomicExpr::AO__c11_atomic_compare_exchange_strong:
  case AtomicExpr::AO__c11_atomic_compare_exchange_weak:
  case AtomicExpr::AO__atomic_compare_exchange_n:
  case AtomicExpr::AO__atomic_compare_exchange:
    Val1 = EmitScalarExpr(E->getVal1());
    if (E->getOp() == AtomicExpr::AO__atomic_compare_exchange)
      Val2 = EmitScalarExpr(E->getVal2());
    else
      Val2 = EmitValToTemp(*this, E->getVal2());
    OrderFail = EmitScalarExpr(E->getOrderFail());
    if (E->getNumSubExprs() == 6)
      IsWeak = EmitScalarExpr(E->getWeak());
    break;

  case AtomicExpr::AO__c11_atomic_fetch_add:
  case AtomicExpr::AO__c11_atomic_fetch_sub:
    if (MemTy->isPointerType()) {
      // For pointer arithmetic, we're required to do a bit of math:
      // adding 1 to an int* is not the same as adding 1 to a uintptr_t.
      // ... but only for the C11 builtins. The GNU builtins expect the
      // user to multiply by sizeof(T).
      QualType Val1Ty = E->getVal1()->getType();
      llvm::Value *Val1Scalar = EmitScalarExpr(E->getVal1());
      CharUnits PointeeIncAmt =
          getContext().getTypeSizeInChars(MemTy->getPointeeType());
      Val1Scalar = Builder.CreateMul(Val1Scalar, CGM.getSize(PointeeIncAmt));
      Val1 = CreateMemTemp(Val1Ty, ".atomictmp");
      EmitStoreOfScalar(Val1Scalar, MakeAddrLValue(Val1, Val1Ty));
      break;
    }
    // Fall through.
  case AtomicExpr::AO__atomic_fetch_add:
  case AtomicExpr::AO__atomic_fetch_sub:
  case AtomicExpr::AO__atomic_add_fetch:
  case AtomicExpr::AO__atomic_sub_fetch:
  case AtomicExpr::AO__c11_atomic_store:
  case AtomicExpr::AO__c11_atomic_exchange:
  case AtomicExpr::AO__atomic_store_n:
  case AtomicExpr::AO__atomic_exchange_n:
  case AtomicExpr::AO__c11_atomic_fetch_and:
  case AtomicExpr::AO__c11_atomic_fetch_or:
  case AtomicExpr::AO__c11_atomic_fetch_xor:
  case AtomicExpr::AO__atomic_fetch_and:
  case AtomicExpr::AO__atomic_fetch_or:
  case AtomicExpr::AO__atomic_fetch_xor:
  case AtomicExpr::AO__atomic_fetch_nand:
  case AtomicExpr::AO__atomic_and_fetch:
  case AtomicExpr::AO__atomic_or_fetch:
  case AtomicExpr::AO__atomic_xor_fetch:
  case AtomicExpr::AO__atomic_nand_fetch:
    Val1 = EmitValToTemp(*this, E->getVal1());
    break;
  }

  QualType RValTy = E->getType().getUnqualifiedType();

  auto GetDest = [&] {
    if (!RValTy->isVoidType() && !Dest) {
      Dest = CreateMemTemp(RValTy, ".atomicdst");
    }
    return Dest;
  };

  // Use a library call.  See: http://gcc.gnu.org/wiki/Atomic/GCCMM/LIbrary .
  if (UseLibcall) {
    bool UseOptimizedLibcall = false;
    switch (E->getOp()) {
    case AtomicExpr::AO__c11_atomic_fetch_add:
    case AtomicExpr::AO__atomic_fetch_add:
    case AtomicExpr::AO__c11_atomic_fetch_and:
    case AtomicExpr::AO__atomic_fetch_and:
    case AtomicExpr::AO__c11_atomic_fetch_or:
    case AtomicExpr::AO__atomic_fetch_or:
    case AtomicExpr::AO__c11_atomic_fetch_sub:
    case AtomicExpr::AO__atomic_fetch_sub:
    case AtomicExpr::AO__c11_atomic_fetch_xor:
    case AtomicExpr::AO__atomic_fetch_xor:
      // For these, only library calls for certain sizes exist.
      UseOptimizedLibcall = true;
      break;
    default:
      // Only use optimized library calls for sizes for which they exist.
      if (Size == 1 || Size == 2 || Size == 4 || Size == 8)
        UseOptimizedLibcall = true;
      break;
    }

    CallArgList Args;
    if (!UseOptimizedLibcall) {
      // For non-optimized library calls, the size is the first parameter
      Args.add(RValue::get(llvm::ConstantInt::get(SizeTy, Size)),
               getContext().getSizeType());
    }
    // Atomic address is the first or second parameter
    Args.add(RValue::get(EmitCastToVoidPtr(Ptr)), getContext().VoidPtrTy);

    std::string LibCallName;
    QualType LoweredMemTy =
      MemTy->isPointerType() ? getContext().getIntPtrType() : MemTy;
    QualType RetTy;
    bool HaveRetTy = false;
    switch (E->getOp()) {
    // There is only one libcall for compare an exchange, because there is no
    // optimisation benefit possible from a libcall version of a weak compare
    // and exchange.
    // bool __atomic_compare_exchange(size_t size, void *mem, void *expected,
    //                                void *desired, int success, int failure)
    // bool __atomic_compare_exchange_N(T *mem, T *expected, T desired,
    //                                  int success, int failure)
    case AtomicExpr::AO__c11_atomic_compare_exchange_weak:
    case AtomicExpr::AO__c11_atomic_compare_exchange_strong:
    case AtomicExpr::AO__atomic_compare_exchange:
    case AtomicExpr::AO__atomic_compare_exchange_n:
      LibCallName = "__atomic_compare_exchange";
      RetTy = getContext().BoolTy;
      HaveRetTy = true;
      Args.add(RValue::get(EmitCastToVoidPtr(Val1)), getContext().VoidPtrTy);
      AddDirectArgument(*this, Args, UseOptimizedLibcall, Val2, MemTy,
                        E->getExprLoc(), sizeChars);
      Args.add(RValue::get(Order), getContext().IntTy);
      Order = OrderFail;
      break;
    // void __atomic_exchange(size_t size, void *mem, void *val, void *return,
    //                        int order)
    // T __atomic_exchange_N(T *mem, T val, int order)
    case AtomicExpr::AO__c11_atomic_exchange:
    case AtomicExpr::AO__atomic_exchange_n:
    case AtomicExpr::AO__atomic_exchange:
      LibCallName = "__atomic_exchange";
      AddDirectArgument(*this, Args, UseOptimizedLibcall, Val1, MemTy,
                        E->getExprLoc(), sizeChars);
      break;
    // void __atomic_store(size_t size, void *mem, void *val, int order)
    // void __atomic_store_N(T *mem, T val, int order)
    case AtomicExpr::AO__c11_atomic_store:
    case AtomicExpr::AO__atomic_store:
    case AtomicExpr::AO__atomic_store_n:
      LibCallName = "__atomic_store";
      RetTy = getContext().VoidTy;
      HaveRetTy = true;
      AddDirectArgument(*this, Args, UseOptimizedLibcall, Val1, MemTy,
                        E->getExprLoc(), sizeChars);
      break;
    // void __atomic_load(size_t size, void *mem, void *return, int order)
    // T __atomic_load_N(T *mem, int order)
    case AtomicExpr::AO__c11_atomic_load:
    case AtomicExpr::AO__atomic_load:
    case AtomicExpr::AO__atomic_load_n:
      LibCallName = "__atomic_load";
      break;
    // T __atomic_fetch_add_N(T *mem, T val, int order)
    case AtomicExpr::AO__c11_atomic_fetch_add:
    case AtomicExpr::AO__atomic_fetch_add:
      LibCallName = "__atomic_fetch_add";
      AddDirectArgument(*this, Args, UseOptimizedLibcall, Val1, LoweredMemTy,
                        E->getExprLoc(), sizeChars);
      break;
    // T __atomic_fetch_and_N(T *mem, T val, int order)
    case AtomicExpr::AO__c11_atomic_fetch_and:
    case AtomicExpr::AO__atomic_fetch_and:
      LibCallName = "__atomic_fetch_and";
      AddDirectArgument(*this, Args, UseOptimizedLibcall, Val1, MemTy,
                        E->getExprLoc(), sizeChars);
      break;
    // T __atomic_fetch_or_N(T *mem, T val, int order)
    case AtomicExpr::AO__c11_atomic_fetch_or:
    case AtomicExpr::AO__atomic_fetch_or:
      LibCallName = "__atomic_fetch_or";
      AddDirectArgument(*this, Args, UseOptimizedLibcall, Val1, MemTy,
                        E->getExprLoc(), sizeChars);
      break;
    // T __atomic_fetch_sub_N(T *mem, T val, int order)
    case AtomicExpr::AO__c11_atomic_fetch_sub:
    case AtomicExpr::AO__atomic_fetch_sub:
      LibCallName = "__atomic_fetch_sub";
      AddDirectArgument(*this, Args, UseOptimizedLibcall, Val1, LoweredMemTy,
                        E->getExprLoc(), sizeChars);
      break;
    // T __atomic_fetch_xor_N(T *mem, T val, int order)
    case AtomicExpr::AO__c11_atomic_fetch_xor:
    case AtomicExpr::AO__atomic_fetch_xor:
      LibCallName = "__atomic_fetch_xor";
      AddDirectArgument(*this, Args, UseOptimizedLibcall, Val1, MemTy,
                        E->getExprLoc(), sizeChars);
      break;
    default: return EmitUnsupportedRValue(E, "atomic library call");
    }

    // Optimized functions have the size in their name.
    if (UseOptimizedLibcall)
      LibCallName += "_" + llvm::utostr(Size);
    // By default, assume we return a value of the atomic type.
    if (!HaveRetTy) {
      if (UseOptimizedLibcall) {
        // Value is returned directly.
        // The function returns an appropriately sized integer type.
        RetTy = getContext().getIntTypeForBitwidth(
            getContext().toBits(sizeChars), /*Signed=*/false);
      } else {
        // Value is returned through parameter before the order.
        RetTy = getContext().VoidTy;
        Args.add(RValue::get(EmitCastToVoidPtr(Dest)), getContext().VoidPtrTy);
      }
    }
    // order is always the last parameter
    Args.add(RValue::get(Order),
             getContext().IntTy);

    RValue Res = emitAtomicLibcall(*this, LibCallName, RetTy, Args);
    // The value is returned directly from the libcall.
    if (HaveRetTy && !RetTy->isVoidType())
      return Res;
    // The value is returned via an explicit out param.
    if (RetTy->isVoidType())
      return RValue::get(nullptr);
    // The value is returned directly for optimized libcalls but the caller is
    // expected an out-param.
    if (UseOptimizedLibcall) {
      llvm::Value *ResVal = Res.getScalarVal();
      llvm::StoreInst *StoreDest = Builder.CreateStore(
          ResVal,
          Builder.CreateBitCast(GetDest(), ResVal->getType()->getPointerTo()));
      StoreDest->setAlignment(Align);
    }
    return convertTempToRValue(Dest, RValTy, E->getExprLoc());
  }

  bool IsStore = E->getOp() == AtomicExpr::AO__c11_atomic_store ||
                 E->getOp() == AtomicExpr::AO__atomic_store ||
                 E->getOp() == AtomicExpr::AO__atomic_store_n;
  bool IsLoad = E->getOp() == AtomicExpr::AO__c11_atomic_load ||
                E->getOp() == AtomicExpr::AO__atomic_load ||
                E->getOp() == AtomicExpr::AO__atomic_load_n;

  llvm::Type *ITy =
      llvm::IntegerType::get(getLLVMContext(), Size * 8);
  llvm::Value *OrigDest = GetDest();
  Ptr = Builder.CreateBitCast(
      Ptr, ITy->getPointerTo(Ptr->getType()->getPointerAddressSpace()));
  if (Val1) Val1 = Builder.CreateBitCast(Val1, ITy->getPointerTo());
  if (Val2) Val2 = Builder.CreateBitCast(Val2, ITy->getPointerTo());
  if (Dest && !E->isCmpXChg())
    Dest = Builder.CreateBitCast(Dest, ITy->getPointerTo());

  if (isa<llvm::ConstantInt>(Order)) {
    int ord = cast<llvm::ConstantInt>(Order)->getZExtValue();
    switch (ord) {
    case AtomicExpr::AO_ABI_memory_order_relaxed:
      EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, IsWeak, OrderFail,
                   Size, Align, llvm::Monotonic);
      break;
    case AtomicExpr::AO_ABI_memory_order_consume:
    case AtomicExpr::AO_ABI_memory_order_acquire:
      if (IsStore)
        break; // Avoid crashing on code with undefined behavior
      EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, IsWeak, OrderFail,
                   Size, Align, llvm::Acquire);
      break;
    case AtomicExpr::AO_ABI_memory_order_release:
      if (IsLoad)
        break; // Avoid crashing on code with undefined behavior
      EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, IsWeak, OrderFail,
                   Size, Align, llvm::Release);
      break;
    case AtomicExpr::AO_ABI_memory_order_acq_rel:
      if (IsLoad || IsStore)
        break; // Avoid crashing on code with undefined behavior
      EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, IsWeak, OrderFail,
                   Size, Align, llvm::AcquireRelease);
      break;
    case AtomicExpr::AO_ABI_memory_order_seq_cst:
      EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, IsWeak, OrderFail,
                   Size, Align, llvm::SequentiallyConsistent);
      break;
    default: // invalid order
      // We should not ever get here normally, but it's hard to
      // enforce that in general.
      break;
    }
    if (RValTy->isVoidType())
      return RValue::get(nullptr);
    return convertTempToRValue(OrigDest, RValTy, E->getExprLoc());
  }

  // Long case, when Order isn't obviously constant.

  // Create all the relevant BB's
  llvm::BasicBlock *MonotonicBB = nullptr, *AcquireBB = nullptr,
                   *ReleaseBB = nullptr, *AcqRelBB = nullptr,
                   *SeqCstBB = nullptr;
  MonotonicBB = createBasicBlock("monotonic", CurFn);
  if (!IsStore)
    AcquireBB = createBasicBlock("acquire", CurFn);
  if (!IsLoad)
    ReleaseBB = createBasicBlock("release", CurFn);
  if (!IsLoad && !IsStore)
    AcqRelBB = createBasicBlock("acqrel", CurFn);
  SeqCstBB = createBasicBlock("seqcst", CurFn);
  llvm::BasicBlock *ContBB = createBasicBlock("atomic.continue", CurFn);

  // Create the switch for the split
  // MonotonicBB is arbitrarily chosen as the default case; in practice, this
  // doesn't matter unless someone is crazy enough to use something that
  // doesn't fold to a constant for the ordering.
  Order = Builder.CreateIntCast(Order, Builder.getInt32Ty(), false);
  llvm::SwitchInst *SI = Builder.CreateSwitch(Order, MonotonicBB);

  // Emit all the different atomics
  Builder.SetInsertPoint(MonotonicBB);
  EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, IsWeak, OrderFail,
               Size, Align, llvm::Monotonic);
  Builder.CreateBr(ContBB);
  if (!IsStore) {
    Builder.SetInsertPoint(AcquireBB);
    EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, IsWeak, OrderFail,
                 Size, Align, llvm::Acquire);
    Builder.CreateBr(ContBB);
    SI->addCase(Builder.getInt32(AtomicExpr::AO_ABI_memory_order_consume),
                AcquireBB);
    SI->addCase(Builder.getInt32(AtomicExpr::AO_ABI_memory_order_acquire),
                AcquireBB);
  }
  if (!IsLoad) {
    Builder.SetInsertPoint(ReleaseBB);
    EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, IsWeak, OrderFail,
                 Size, Align, llvm::Release);
    Builder.CreateBr(ContBB);
    SI->addCase(Builder.getInt32(AtomicExpr::AO_ABI_memory_order_release),
                ReleaseBB);
  }
  if (!IsLoad && !IsStore) {
    Builder.SetInsertPoint(AcqRelBB);
    EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, IsWeak, OrderFail,
                 Size, Align, llvm::AcquireRelease);
    Builder.CreateBr(ContBB);
    SI->addCase(Builder.getInt32(AtomicExpr::AO_ABI_memory_order_acq_rel),
                AcqRelBB);
  }
  Builder.SetInsertPoint(SeqCstBB);
  EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, IsWeak, OrderFail,
               Size, Align, llvm::SequentiallyConsistent);
  Builder.CreateBr(ContBB);
  SI->addCase(Builder.getInt32(AtomicExpr::AO_ABI_memory_order_seq_cst),
              SeqCstBB);

  // Cleanup and return
  Builder.SetInsertPoint(ContBB);
  if (RValTy->isVoidType())
    return RValue::get(nullptr);
  return convertTempToRValue(OrigDest, RValTy, E->getExprLoc());
}

llvm::Value *AtomicInfo::emitCastToAtomicIntPointer(llvm::Value *addr) const {
  unsigned addrspace =
    cast<llvm::PointerType>(addr->getType())->getAddressSpace();
  llvm::IntegerType *ty =
    llvm::IntegerType::get(CGF.getLLVMContext(), AtomicSizeInBits);
  return CGF.Builder.CreateBitCast(addr, ty->getPointerTo(addrspace));
}

RValue AtomicInfo::convertTempToRValue(llvm::Value *addr,
                                       AggValueSlot resultSlot,
                                       SourceLocation loc) const {
  if (LVal.isSimple()) {
    if (EvaluationKind == TEK_Aggregate)
      return resultSlot.asRValue();

    // Drill into the padding structure if we have one.
    if (hasPadding())
      addr = CGF.Builder.CreateStructGEP(addr, 0);

    // Otherwise, just convert the temporary to an r-value using the
    // normal conversion routine.
    return CGF.convertTempToRValue(addr, getValueType(), loc);
  } else if (LVal.isBitField())
    return CGF.EmitLoadOfBitfieldLValue(LValue::MakeBitfield(
        addr, LVal.getBitFieldInfo(), LVal.getType(), LVal.getAlignment()));
  else if (LVal.isVectorElt())
    return CGF.EmitLoadOfLValue(LValue::MakeVectorElt(addr, LVal.getVectorIdx(),
                                                      LVal.getType(),
                                                      LVal.getAlignment()),
                                loc);
  assert(LVal.isExtVectorElt());
  return CGF.EmitLoadOfExtVectorElementLValue(LValue::MakeExtVectorElt(
      addr, LVal.getExtVectorElts(), LVal.getType(), LVal.getAlignment()));
}

RValue AtomicInfo::convertIntToValue(llvm::Value *IntVal,
                                     AggValueSlot ResultSlot,
                                     SourceLocation Loc) const {
  assert(LVal.isSimple());
  // Try not to in some easy cases.
  assert(IntVal->getType()->isIntegerTy() && "Expected integer value");
  if (getEvaluationKind() == TEK_Scalar && !hasPadding()) {
    auto *ValTy = CGF.ConvertTypeForMem(ValueTy);
    if (ValTy->isIntegerTy()) {
      assert(IntVal->getType() == ValTy && "Different integer types.");
      return RValue::get(CGF.EmitFromMemory(IntVal, ValueTy));
    } else if (ValTy->isPointerTy())
      return RValue::get(CGF.Builder.CreateIntToPtr(IntVal, ValTy));
    else if (llvm::CastInst::isBitCastable(IntVal->getType(), ValTy))
      return RValue::get(CGF.Builder.CreateBitCast(IntVal, ValTy));
  }

  // Create a temporary.  This needs to be big enough to hold the
  // atomic integer.
  llvm::Value *Temp;
  bool TempIsVolatile = false;
  CharUnits TempAlignment;
  if (getEvaluationKind() == TEK_Aggregate) {
    assert(!ResultSlot.isIgnored());
    Temp = ResultSlot.getAddr();
    TempAlignment = getValueAlignment();
    TempIsVolatile = ResultSlot.isVolatile();
  } else {
    Temp = CGF.CreateMemTemp(getAtomicType(), "atomic-temp");
    TempAlignment = getAtomicAlignment();
  }

  // Slam the integer into the temporary.
  llvm::Value *CastTemp = emitCastToAtomicIntPointer(Temp);
  CGF.Builder.CreateAlignedStore(IntVal, CastTemp, TempAlignment.getQuantity())
      ->setVolatile(TempIsVolatile);

  return convertTempToRValue(Temp, ResultSlot, Loc);
}

/// An LValue is a candidate for having its loads and stores be made atomic if
/// we are operating under /volatile:ms *and* the LValue itself is volatile and
/// performing such an operation can be performed without a libcall.
bool CodeGenFunction::LValueIsSuitableForInlineAtomic(LValue LV) {
  AtomicInfo AI(*this, LV);
  bool IsVolatile = LV.isVolatile() || hasVolatileMember(LV.getType());
  // An atomic is inline if we don't need to use a libcall.
  bool AtomicIsInline = !AI.shouldUseLibcall();
  return CGM.getCodeGenOpts().MSVolatile && IsVolatile && AtomicIsInline;
}

/// An type is a candidate for having its loads and stores be made atomic if
/// we are operating under /volatile:ms *and* we know the access is volatile and
/// performing such an operation can be performed without a libcall.
bool CodeGenFunction::typeIsSuitableForInlineAtomic(QualType Ty,
                                                    bool IsVolatile) const {
  // An atomic is inline if we don't need to use a libcall (e.g. it is builtin).
  bool AtomicIsInline = getContext().getTargetInfo().hasBuiltinAtomic(
      getContext().getTypeSize(Ty), getContext().getTypeAlign(Ty));
  return CGM.getCodeGenOpts().MSVolatile && IsVolatile && AtomicIsInline;
}

RValue CodeGenFunction::EmitAtomicLoad(LValue LV, SourceLocation SL,
                                       AggValueSlot Slot) {
  llvm::AtomicOrdering AO;
  bool IsVolatile = LV.isVolatileQualified();
  if (LV.getType()->isAtomicType()) {
    AO = llvm::SequentiallyConsistent;
  } else {
    AO = llvm::Acquire;
    IsVolatile = true;
  }
  return EmitAtomicLoad(LV, SL, AO, IsVolatile, Slot);
}

/// Emit a load from an l-value of atomic type.  Note that the r-value
/// we produce is an r-value of the atomic *value* type.
RValue CodeGenFunction::EmitAtomicLoad(LValue src, SourceLocation loc,
                                       llvm::AtomicOrdering AO, bool IsVolatile,
                                       AggValueSlot resultSlot) {
  AtomicInfo atomics(*this, src);
  LValue LVal = atomics.getAtomicLValue();
  llvm::Value *SrcAddr = nullptr;
  llvm::AllocaInst *NonSimpleTempAlloca = nullptr;
  if (LVal.isSimple())
    SrcAddr = LVal.getAddress();
  else {
    if (LVal.isBitField())
      SrcAddr = LVal.getBitFieldAddr();
    else if (LVal.isVectorElt())
      SrcAddr = LVal.getVectorAddr();
    else {
      assert(LVal.isExtVectorElt());
      SrcAddr = LVal.getExtVectorAddr();
    }
    NonSimpleTempAlloca = CreateTempAlloca(
        SrcAddr->getType()->getPointerElementType(), "atomic-load-temp");
    NonSimpleTempAlloca->setAlignment(getContext().toBits(src.getAlignment()));
  }

  // Check whether we should use a library call.
  if (atomics.shouldUseLibcall()) {
    llvm::Value *tempAddr;
    if (LVal.isSimple()) {
      if (!resultSlot.isIgnored()) {
        assert(atomics.getEvaluationKind() == TEK_Aggregate);
        tempAddr = resultSlot.getAddr();
      } else
        tempAddr = CreateMemTemp(atomics.getAtomicType(), "atomic-load-temp");
    } else
      tempAddr = NonSimpleTempAlloca;

    // void __atomic_load(size_t size, void *mem, void *return, int order);
    CallArgList args;
    args.add(RValue::get(atomics.getAtomicSizeValue()),
             getContext().getSizeType());
    args.add(RValue::get(EmitCastToVoidPtr(SrcAddr)), getContext().VoidPtrTy);
    args.add(RValue::get(EmitCastToVoidPtr(tempAddr)), getContext().VoidPtrTy);
    args.add(RValue::get(llvm::ConstantInt::get(
                 IntTy, AtomicExpr::AO_ABI_memory_order_seq_cst)),
             getContext().IntTy);
    emitAtomicLibcall(*this, "__atomic_load", getContext().VoidTy, args);

    // Produce the r-value.
    return atomics.convertTempToRValue(tempAddr, resultSlot, loc);
  }

  // Okay, we're doing this natively.
  llvm::Value *addr = atomics.emitCastToAtomicIntPointer(SrcAddr);
  llvm::LoadInst *load = Builder.CreateLoad(addr, "atomic-load");
  load->setAtomic(AO);

  // Other decoration.
  load->setAlignment(src.getAlignment().getQuantity());
  if (IsVolatile)
    load->setVolatile(true);
  if (src.getTBAAInfo())
    CGM.DecorateInstruction(load, src.getTBAAInfo());

  // If we're ignoring an aggregate return, don't do anything.
  if (atomics.getEvaluationKind() == TEK_Aggregate && resultSlot.isIgnored())
    return RValue::getAggregate(nullptr, false);

  // Okay, turn that back into the original value type.
  if (src.isSimple())
    return atomics.convertIntToValue(load, resultSlot, loc);

  auto *IntAddr = atomics.emitCastToAtomicIntPointer(NonSimpleTempAlloca);
  Builder.CreateAlignedStore(load, IntAddr, src.getAlignment().getQuantity());
  return atomics.convertTempToRValue(NonSimpleTempAlloca, resultSlot, loc);
}


/// Copy an r-value into memory as part of storing to an atomic type.
/// This needs to create a bit-pattern suitable for atomic operations.
void AtomicInfo::emitCopyIntoMemory(RValue rvalue) const {
  assert(LVal.isSimple());
  // If we have an r-value, the rvalue should be of the atomic type,
  // which means that the caller is responsible for having zeroed
  // any padding.  Just do an aggregate copy of that type.
  if (rvalue.isAggregate()) {
    CGF.EmitAggregateCopy(LVal.getAddress(),
                          rvalue.getAggregateAddr(),
                          getAtomicType(),
                          (rvalue.isVolatileQualified()
                           || LVal.isVolatileQualified()),
                          LVal.getAlignment());
    return;
  }

  // Okay, otherwise we're copying stuff.

  // Zero out the buffer if necessary.
  emitMemSetZeroIfNecessary();

  // Drill past the padding if present.
  LValue TempLVal = projectValue();

  // Okay, store the rvalue in.
  if (rvalue.isScalar()) {
    CGF.EmitStoreOfScalar(rvalue.getScalarVal(), TempLVal, /*init*/ true);
  } else {
    CGF.EmitStoreOfComplex(rvalue.getComplexVal(), TempLVal, /*init*/ true);
  }
}


/// Materialize an r-value into memory for the purposes of storing it
/// to an atomic type.
llvm::Value *AtomicInfo::materializeRValue(RValue rvalue) const {
  // Aggregate r-values are already in memory, and EmitAtomicStore
  // requires them to be values of the atomic type.
  if (rvalue.isAggregate())
    return rvalue.getAggregateAddr();

  // Otherwise, make a temporary and materialize into it.
  llvm::Value *temp = CGF.CreateMemTemp(getAtomicType(), "atomic-store-temp");
  LValue tempLV =
      CGF.MakeAddrLValue(temp, getAtomicType(), getAtomicAlignment());
  AtomicInfo Atomics(CGF, tempLV);
  Atomics.emitCopyIntoMemory(rvalue);
  return temp;
}

llvm::Value *AtomicInfo::convertRValueToInt(RValue RVal) const {
  // If we've got a scalar value of the right size, try to avoid going
  // through memory.
  if (RVal.isScalar() && !hasPadding()) {
    llvm::Value *Value = RVal.getScalarVal();
    if (isa<llvm::IntegerType>(Value->getType()))
      return Value;
    else {
      llvm::IntegerType *InputIntTy =
          llvm::IntegerType::get(CGF.getLLVMContext(), getValueSizeInBits());
      if (isa<llvm::PointerType>(Value->getType()))
        return CGF.Builder.CreatePtrToInt(Value, InputIntTy);
      else if (llvm::BitCastInst::isBitCastable(Value->getType(), InputIntTy))
        return CGF.Builder.CreateBitCast(Value, InputIntTy);
    }
  }
  // Otherwise, we need to go through memory.
  // Put the r-value in memory.
  llvm::Value *Addr = materializeRValue(RVal);

  // Cast the temporary to the atomic int type and pull a value out.
  Addr = emitCastToAtomicIntPointer(Addr);
  return CGF.Builder.CreateAlignedLoad(Addr,
                                       getAtomicAlignment().getQuantity());
}

void CodeGenFunction::EmitAtomicStore(RValue rvalue, LValue lvalue,
                                      bool isInit) {
  bool IsVolatile = lvalue.isVolatileQualified();
  llvm::AtomicOrdering AO;
  if (lvalue.getType()->isAtomicType()) {
    AO = llvm::SequentiallyConsistent;
  } else {
    AO = llvm::Release;
    IsVolatile = true;
  }
  return EmitAtomicStore(rvalue, lvalue, AO, IsVolatile, isInit);
}

/// Emit a store to an l-value of atomic type.
///
/// Note that the r-value is expected to be an r-value *of the atomic
/// type*; this means that for aggregate r-values, it should include
/// storage for any padding that was necessary.
void CodeGenFunction::EmitAtomicStore(RValue rvalue, LValue dest,
                                      llvm::AtomicOrdering AO, bool IsVolatile,
                                      bool isInit) {
  // If this is an aggregate r-value, it should agree in type except
  // maybe for address-space qualification.
  assert(!rvalue.isAggregate() ||
         rvalue.getAggregateAddr()->getType()->getPointerElementType()
           == dest.getAddress()->getType()->getPointerElementType());

  AtomicInfo atomics(*this, dest);

  // If this is an initialization, just put the value there normally.
  if (isInit) {
    atomics.emitCopyIntoMemory(rvalue);
    return;
  }

  // Check whether we should use a library call.
  if (atomics.shouldUseLibcall()) {
    // Produce a source address.
    llvm::Value *srcAddr = atomics.materializeRValue(rvalue);

    // void __atomic_store(size_t size, void *mem, void *val, int order)
    CallArgList args;
    args.add(RValue::get(atomics.getAtomicSizeValue()),
             getContext().getSizeType());
    args.add(RValue::get(EmitCastToVoidPtr(dest.getAddress())),
             getContext().VoidPtrTy);
    args.add(RValue::get(EmitCastToVoidPtr(srcAddr)),
             getContext().VoidPtrTy);
    args.add(RValue::get(llvm::ConstantInt::get(
                 IntTy, AtomicExpr::AO_ABI_memory_order_seq_cst)),
             getContext().IntTy);
    emitAtomicLibcall(*this, "__atomic_store", getContext().VoidTy, args);
    return;
  }

  // Okay, we're doing this natively.
  llvm::Value *intValue = atomics.convertRValueToInt(rvalue);

  // Do the atomic store.
  llvm::Value *addr = atomics.emitCastToAtomicIntPointer(dest.getAddress());
  llvm::StoreInst *store = Builder.CreateStore(intValue, addr);

  // Initializations don't need to be atomic.
  if (!isInit) store->setAtomic(AO);

  // Other decoration.
  store->setAlignment(dest.getAlignment().getQuantity());
  if (IsVolatile)
    store->setVolatile(true);
  if (dest.getTBAAInfo())
    CGM.DecorateInstruction(store, dest.getTBAAInfo());
}

/// Emit a compare-and-exchange op for atomic type.
///
std::pair<RValue, RValue> CodeGenFunction::EmitAtomicCompareExchange(
    LValue Obj, RValue Expected, RValue Desired, SourceLocation Loc,
    llvm::AtomicOrdering Success, llvm::AtomicOrdering Failure, bool IsWeak,
    AggValueSlot Slot) {
  // If this is an aggregate r-value, it should agree in type except
  // maybe for address-space qualification.
  assert(!Expected.isAggregate() ||
         Expected.getAggregateAddr()->getType()->getPointerElementType() ==
             Obj.getAddress()->getType()->getPointerElementType());
  assert(!Desired.isAggregate() ||
         Desired.getAggregateAddr()->getType()->getPointerElementType() ==
             Obj.getAddress()->getType()->getPointerElementType());
  AtomicInfo Atomics(*this, Obj);

  if (Failure >= Success)
    // Don't assert on undefined behavior.
    Failure = llvm::AtomicCmpXchgInst::getStrongestFailureOrdering(Success);

  auto Alignment = Atomics.getValueAlignment();
  // Check whether we should use a library call.
  if (Atomics.shouldUseLibcall()) {
    auto *ExpectedAddr = Atomics.materializeRValue(Expected);
    // Produce a source address.
    auto *DesiredAddr = Atomics.materializeRValue(Desired);
    // bool __atomic_compare_exchange(size_t size, void *obj, void *expected,
    // void *desired, int success, int failure);
    CallArgList Args;
    Args.add(RValue::get(Atomics.getAtomicSizeValue()),
             getContext().getSizeType());
    Args.add(RValue::get(EmitCastToVoidPtr(Obj.getAddress())),
             getContext().VoidPtrTy);
    Args.add(RValue::get(EmitCastToVoidPtr(ExpectedAddr)),
             getContext().VoidPtrTy);
    Args.add(RValue::get(EmitCastToVoidPtr(DesiredAddr)),
             getContext().VoidPtrTy);
    Args.add(RValue::get(llvm::ConstantInt::get(IntTy, Success)),
             getContext().IntTy);
    Args.add(RValue::get(llvm::ConstantInt::get(IntTy, Failure)),
             getContext().IntTy);
    auto SuccessFailureRVal = emitAtomicLibcall(
        *this, "__atomic_compare_exchange", getContext().BoolTy, Args);
    auto *PreviousVal =
        Builder.CreateAlignedLoad(ExpectedAddr, Alignment.getQuantity());
    return std::make_pair(RValue::get(PreviousVal), SuccessFailureRVal);
  }

  // If we've got a scalar value of the right size, try to avoid going
  // through memory.
  auto *ExpectedIntVal = Atomics.convertRValueToInt(Expected);
  auto *DesiredIntVal = Atomics.convertRValueToInt(Desired);

  // Do the atomic store.
  auto *Addr = Atomics.emitCastToAtomicIntPointer(Obj.getAddress());
  auto *Inst = Builder.CreateAtomicCmpXchg(Addr, ExpectedIntVal, DesiredIntVal,
                                          Success, Failure);
  // Other decoration.
  Inst->setVolatile(Obj.isVolatileQualified());
  Inst->setWeak(IsWeak);

  // Okay, turn that back into the original value type.
  auto *PreviousVal = Builder.CreateExtractValue(Inst, /*Idxs=*/0);
  auto *SuccessFailureVal = Builder.CreateExtractValue(Inst, /*Idxs=*/1);
  return std::make_pair(Atomics.convertIntToValue(PreviousVal, Slot, Loc),
                        RValue::get(SuccessFailureVal));
}

void CodeGenFunction::EmitAtomicInit(Expr *init, LValue dest) {
  AtomicInfo atomics(*this, dest);

  switch (atomics.getEvaluationKind()) {
  case TEK_Scalar: {
    llvm::Value *value = EmitScalarExpr(init);
    atomics.emitCopyIntoMemory(RValue::get(value));
    return;
  }

  case TEK_Complex: {
    ComplexPairTy value = EmitComplexExpr(init);
    atomics.emitCopyIntoMemory(RValue::getComplex(value));
    return;
  }

  case TEK_Aggregate: {
    // Fix up the destination if the initializer isn't an expression
    // of atomic type.
    bool Zeroed = false;
    if (!init->getType()->isAtomicType()) {
      Zeroed = atomics.emitMemSetZeroIfNecessary();
      dest = atomics.projectValue();
    }

    // Evaluate the expression directly into the destination.
    AggValueSlot slot = AggValueSlot::forLValue(dest,
                                        AggValueSlot::IsNotDestructed,
                                        AggValueSlot::DoesNotNeedGCBarriers,
                                        AggValueSlot::IsNotAliased,
                                        Zeroed ? AggValueSlot::IsZeroed :
                                                 AggValueSlot::IsNotZeroed);

    EmitAggExpr(init, slot);
    return;
  }
  }
  llvm_unreachable("bad evaluation kind");
}