vendor/clang/clang-trunk-r178860

1 files changed, 942 insertions, 0 deletions

diff --git a/lib/CodeGen/CGAtomic.cpp b/lib/CodeGen/CGAtomic.cpp
new file mode 100644
index 000000000000..817d5c4cc687
--- /dev/null
+++ b/lib/CodeGen/CGAtomic.cpp
@@ -0,0 +1,942 @@
+//===--- 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 "CodeGenModule.h"
+#include "clang/AST/ASTContext.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Operator.h"
+
+using namespace clang;
+using namespace CodeGen;
+
+// The ABI values for various atomic memory orderings.
+enum AtomicOrderingKind {
+  AO_ABI_memory_order_relaxed = 0,
+  AO_ABI_memory_order_consume = 1,
+  AO_ABI_memory_order_acquire = 2,
+  AO_ABI_memory_order_release = 3,
+  AO_ABI_memory_order_acq_rel = 4,
+  AO_ABI_memory_order_seq_cst = 5
+};
+
+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;
+  public:
+    AtomicInfo(CodeGenFunction &CGF, LValue &lvalue) : CGF(CGF) {
+      assert(lvalue.isSimple());
+
+      AtomicTy = lvalue.getType();
+      ValueTy = AtomicTy->castAs<AtomicType>()->getValueType();
+      EvaluationKind = CGF.getEvaluationKind(ValueTy);
+
+      ASTContext &C = CGF.getContext();
+
+      uint64_t valueAlignInBits;
+      llvm::tie(ValueSizeInBits, valueAlignInBits) = C.getTypeInfo(ValueTy);
+
+      uint64_t atomicAlignInBits;
+      llvm::tie(AtomicSizeInBits, atomicAlignInBits) = C.getTypeInfo(AtomicTy);
+
+      assert(ValueSizeInBits <= AtomicSizeInBits);
+      assert(valueAlignInBits <= atomicAlignInBits);
+
+      AtomicAlign = C.toCharUnitsFromBits(atomicAlignInBits);
+      ValueAlign = C.toCharUnitsFromBits(valueAlignInBits);
+      if (lvalue.getAlignment().isZero())
+        lvalue.setAlignment(AtomicAlign);
+
+      UseLibcall =
+        (AtomicSizeInBits > uint64_t(C.toBits(lvalue.getAlignment())) ||
+         AtomicSizeInBits > C.getTargetInfo().getMaxAtomicInlineWidth());
+    }
+
+    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 AtomicSizeInBits; }
+    TypeEvaluationKind getEvaluationKind() const { return EvaluationKind; }
+    bool shouldUseLibcall() const { return UseLibcall; }
+
+    /// 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);
+    }
+
+    void emitMemSetZeroIfNecessary(LValue dest) 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) const;
+
+    /// Copy an atomic r-value into atomic-layout memory.
+    void emitCopyIntoMemory(RValue rvalue, LValue lvalue) const;
+
+    /// Project an l-value down to the value field.
+    LValue projectValue(LValue lvalue) const {
+      llvm::Value *addr = lvalue.getAddress();
+      if (hasPadding())
+        addr = CGF.Builder.CreateStructGEP(addr, 0);
+
+      return LValue::MakeAddr(addr, getValueType(), lvalue.getAlignment(),
+                              CGF.getContext(), lvalue.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);
+
+  // Just be pessimistic about aggregates.
+  case TEK_Aggregate:
+    return true;
+  }
+  llvm_unreachable("bad evaluation kind");
+}
+
+void AtomicInfo::emitMemSetZeroIfNecessary(LValue dest) const {
+  llvm::Value *addr = dest.getAddress();
+  if (!requiresMemSetZero(addr->getType()->getPointerElementType()))
+    return;
+
+  CGF.Builder.CreateMemSet(addr, llvm::ConstantInt::get(CGF.Int8Ty, 0),
+                           AtomicSizeInBits / 8,
+                           dest.getAlignment().getQuantity());
+}
+
+static void
+EmitAtomicOp(CodeGenFunction &CGF, AtomicExpr *E, llvm::Value *Dest,
+             llvm::Value *Ptr, llvm::Value *Val1, llvm::Value *Val2,
+             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:
+  case AtomicExpr::AO__c11_atomic_compare_exchange_weak:
+  case AtomicExpr::AO__atomic_compare_exchange:
+  case AtomicExpr::AO__atomic_compare_exchange_n: {
+    // Note that cmpxchg only supports specifying one ordering and
+    // doesn't support weak cmpxchg, at least at the moment.
+    llvm::LoadInst *LoadVal1 = CGF.Builder.CreateLoad(Val1);
+    LoadVal1->setAlignment(Align);
+    llvm::LoadInst *LoadVal2 = CGF.Builder.CreateLoad(Val2);
+    LoadVal2->setAlignment(Align);
+    llvm::AtomicCmpXchgInst *CXI =
+        CGF.Builder.CreateAtomicCmpXchg(Ptr, LoadVal1, LoadVal2, Order);
+    CXI->setVolatile(E->isVolatile());
+    llvm::StoreInst *StoreVal1 = CGF.Builder.CreateStore(CXI, Val1);
+    StoreVal1->setAlignment(Align);
+    llvm::Value *Cmp = CGF.Builder.CreateICmpEQ(CXI, LoadVal1);
+    CGF.EmitStoreOfScalar(Cmp, CGF.MakeAddrLValue(Dest, E->getType()));
+    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;
+}
+
+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 =
+    getContext().getTargetInfo().getMaxAtomicInlineWidth();
+  bool UseLibcall = (Size != Align ||
+                     getContext().toBits(sizeChars) > MaxInlineWidthInBits);
+
+  llvm::Value *Ptr, *Order, *OrderFail = 0, *Val1 = 0, *Val2 = 0;
+  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(0);
+  }
+
+  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());
+    // Evaluate and discard the 'weak' argument.
+    if (E->getNumSubExprs() == 6)
+      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;
+  }
+
+  if (!E->getType()->isVoidType() && !Dest)
+    Dest = CreateMemTemp(E->getType(), ".atomicdst");
+
+  // Use a library call.  See: http://gcc.gnu.org/wiki/Atomic/GCCMM/LIbrary .
+  if (UseLibcall) {
+
+    SmallVector<QualType, 5> Params;
+    CallArgList Args;
+    // Size is always the first parameter
+    Args.add(RValue::get(llvm::ConstantInt::get(SizeTy, Size)),
+             getContext().getSizeType());
+    // Atomic address is always the second parameter
+    Args.add(RValue::get(EmitCastToVoidPtr(Ptr)),
+             getContext().VoidPtrTy);
+
+    const char* LibCallName;
+    QualType RetTy = getContext().VoidTy;
+    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 *obj, void *expected,
+    //                                void *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;
+      Args.add(RValue::get(EmitCastToVoidPtr(Val1)),
+               getContext().VoidPtrTy);
+      Args.add(RValue::get(EmitCastToVoidPtr(Val2)),
+               getContext().VoidPtrTy);
+      Args.add(RValue::get(Order),
+               getContext().IntTy);
+      Order = OrderFail;
+      break;
+    // void __atomic_exchange(size_t size, void *mem, void *val, void *return,
+    //                        int order)
+    case AtomicExpr::AO__c11_atomic_exchange:
+    case AtomicExpr::AO__atomic_exchange_n:
+    case AtomicExpr::AO__atomic_exchange:
+      LibCallName = "__atomic_exchange";
+      Args.add(RValue::get(EmitCastToVoidPtr(Val1)),
+               getContext().VoidPtrTy);
+      Args.add(RValue::get(EmitCastToVoidPtr(Dest)),
+               getContext().VoidPtrTy);
+      break;
+    // void __atomic_store(size_t size, void *mem, void *val, int order)
+    case AtomicExpr::AO__c11_atomic_store:
+    case AtomicExpr::AO__atomic_store:
+    case AtomicExpr::AO__atomic_store_n:
+      LibCallName = "__atomic_store";
+      Args.add(RValue::get(EmitCastToVoidPtr(Val1)),
+               getContext().VoidPtrTy);
+      break;
+    // void __atomic_load(size_t size, void *mem, void *return, int order)
+    case AtomicExpr::AO__c11_atomic_load:
+    case AtomicExpr::AO__atomic_load:
+    case AtomicExpr::AO__atomic_load_n:
+      LibCallName = "__atomic_load";
+      Args.add(RValue::get(EmitCastToVoidPtr(Dest)),
+               getContext().VoidPtrTy);
+      break;
+#if 0
+    // These are only defined for 1-16 byte integers.  It is not clear what
+    // their semantics would be on anything else...
+    case AtomicExpr::Add:   LibCallName = "__atomic_fetch_add_generic"; break;
+    case AtomicExpr::Sub:   LibCallName = "__atomic_fetch_sub_generic"; break;
+    case AtomicExpr::And:   LibCallName = "__atomic_fetch_and_generic"; break;
+    case AtomicExpr::Or:    LibCallName = "__atomic_fetch_or_generic"; break;
+    case AtomicExpr::Xor:   LibCallName = "__atomic_fetch_xor_generic"; break;
+#endif
+    default: return EmitUnsupportedRValue(E, "atomic library call");
+    }
+    // order is always the last parameter
+    Args.add(RValue::get(Order),
+             getContext().IntTy);
+
+    const CGFunctionInfo &FuncInfo =
+        CGM.getTypes().arrangeFreeFunctionCall(RetTy, Args,
+            FunctionType::ExtInfo(), RequiredArgs::All);
+    llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FuncInfo);
+    llvm::Constant *Func = CGM.CreateRuntimeFunction(FTy, LibCallName);
+    RValue Res = EmitCall(FuncInfo, Func, ReturnValueSlot(), Args);
+    if (E->isCmpXChg())
+      return Res;
+    if (E->getType()->isVoidType())
+      return RValue::get(0);
+    return convertTempToRValue(Dest, E->getType());
+  }
+
+  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 *IPtrTy =
+      llvm::IntegerType::get(getLLVMContext(), Size * 8)->getPointerTo();
+  llvm::Value *OrigDest = Dest;
+  Ptr = Builder.CreateBitCast(Ptr, IPtrTy);
+  if (Val1) Val1 = Builder.CreateBitCast(Val1, IPtrTy);
+  if (Val2) Val2 = Builder.CreateBitCast(Val2, IPtrTy);
+  if (Dest && !E->isCmpXChg()) Dest = Builder.CreateBitCast(Dest, IPtrTy);
+
+  if (isa<llvm::ConstantInt>(Order)) {
+    int ord = cast<llvm::ConstantInt>(Order)->getZExtValue();
+    switch (ord) {
+    case AO_ABI_memory_order_relaxed:
+      EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, Size, Align,
+                   llvm::Monotonic);
+      break;
+    case AO_ABI_memory_order_consume:
+    case AO_ABI_memory_order_acquire:
+      if (IsStore)
+        break; // Avoid crashing on code with undefined behavior
+      EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, Size, Align,
+                   llvm::Acquire);
+      break;
+    case AO_ABI_memory_order_release:
+      if (IsLoad)
+        break; // Avoid crashing on code with undefined behavior
+      EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, Size, Align,
+                   llvm::Release);
+      break;
+    case AO_ABI_memory_order_acq_rel:
+      if (IsLoad || IsStore)
+        break; // Avoid crashing on code with undefined behavior
+      EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, Size, Align,
+                   llvm::AcquireRelease);
+      break;
+    case AO_ABI_memory_order_seq_cst:
+      EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, 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 (E->getType()->isVoidType())
+      return RValue::get(0);
+    return convertTempToRValue(OrigDest, E->getType());
+  }
+
+  // Long case, when Order isn't obviously constant.
+
+  // Create all the relevant BB's
+  llvm::BasicBlock *MonotonicBB = 0, *AcquireBB = 0, *ReleaseBB = 0,
+                   *AcqRelBB = 0, *SeqCstBB = 0;
+  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, Size, Align,
+               llvm::Monotonic);
+  Builder.CreateBr(ContBB);
+  if (!IsStore) {
+    Builder.SetInsertPoint(AcquireBB);
+    EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, Size, Align,
+                 llvm::Acquire);
+    Builder.CreateBr(ContBB);
+    SI->addCase(Builder.getInt32(1), AcquireBB);
+    SI->addCase(Builder.getInt32(2), AcquireBB);
+  }
+  if (!IsLoad) {
+    Builder.SetInsertPoint(ReleaseBB);
+    EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, Size, Align,
+                 llvm::Release);
+    Builder.CreateBr(ContBB);
+    SI->addCase(Builder.getInt32(3), ReleaseBB);
+  }
+  if (!IsLoad && !IsStore) {
+    Builder.SetInsertPoint(AcqRelBB);
+    EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, Size, Align,
+                 llvm::AcquireRelease);
+    Builder.CreateBr(ContBB);
+    SI->addCase(Builder.getInt32(4), AcqRelBB);
+  }
+  Builder.SetInsertPoint(SeqCstBB);
+  EmitAtomicOp(*this, E, Dest, Ptr, Val1, Val2, Size, Align,
+               llvm::SequentiallyConsistent);
+  Builder.CreateBr(ContBB);
+  SI->addCase(Builder.getInt32(5), SeqCstBB);
+
+  // Cleanup and return
+  Builder.SetInsertPoint(ContBB);
+  if (E->getType()->isVoidType())
+    return RValue::get(0);
+  return convertTempToRValue(OrigDest, E->getType());
+}
+
+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) const {
+  if (EvaluationKind == TEK_Aggregate) {
+    // Nothing to do if the result is ignored.
+    if (resultSlot.isIgnored()) return resultSlot.asRValue();
+
+    assert(resultSlot.getAddr() == addr || hasPadding());
+
+    // In these cases, we should have emitted directly into the result slot.
+    if (!hasPadding() || resultSlot.isValueOfAtomic())
+      return resultSlot.asRValue();
+
+    // Otherwise, fall into the common path.
+  }
+
+  // Drill into the padding structure if we have one.
+  if (hasPadding())
+    addr = CGF.Builder.CreateStructGEP(addr, 0);
+
+  // If we're emitting to an aggregate, copy into the result slot.
+  if (EvaluationKind == TEK_Aggregate) {
+    CGF.EmitAggregateCopy(resultSlot.getAddr(), addr, getValueType(),
+                          resultSlot.isVolatile());
+    return resultSlot.asRValue();
+  }
+
+  // Otherwise, just convert the temporary to an r-value using the
+  // normal conversion routine.
+  return CGF.convertTempToRValue(addr, getValueType());
+}
+
+/// 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, AggValueSlot resultSlot) {
+  AtomicInfo atomics(*this, src);
+
+  // Check whether we should use a library call.
+  if (atomics.shouldUseLibcall()) {
+    llvm::Value *tempAddr;
+    if (resultSlot.isValueOfAtomic()) {
+      assert(atomics.getEvaluationKind() == TEK_Aggregate);
+      tempAddr = resultSlot.getPaddedAtomicAddr();
+    } else if (!resultSlot.isIgnored() && !atomics.hasPadding()) {
+      assert(atomics.getEvaluationKind() == TEK_Aggregate);
+      tempAddr = resultSlot.getAddr();
+    } else {
+      tempAddr = CreateMemTemp(atomics.getAtomicType(), "atomic-load-temp");
+    }
+
+    // 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(src.getAddress())),
+             getContext().VoidPtrTy);
+    args.add(RValue::get(EmitCastToVoidPtr(tempAddr)),
+             getContext().VoidPtrTy);
+    args.add(RValue::get(llvm::ConstantInt::get(IntTy,
+                                                AO_ABI_memory_order_seq_cst)),
+             getContext().IntTy);
+    emitAtomicLibcall(*this, "__atomic_load", getContext().VoidTy, args);
+
+    // Produce the r-value.
+    return atomics.convertTempToRValue(tempAddr, resultSlot);
+  }
+
+  // Okay, we're doing this natively.
+  llvm::Value *addr = atomics.emitCastToAtomicIntPointer(src.getAddress());
+  llvm::LoadInst *load = Builder.CreateLoad(addr, "atomic-load");
+  load->setAtomic(llvm::SequentiallyConsistent);
+
+  // Other decoration.
+  load->setAlignment(src.getAlignment().getQuantity());
+  if (src.isVolatileQualified())
+    load->setVolatile(true);
+  if (src.getTBAAInfo())
+    CGM.DecorateInstruction(load, src.getTBAAInfo());
+
+  // Okay, turn that back into the original value type.
+  QualType valueType = atomics.getValueType();
+  llvm::Value *result = load;
+
+  // If we're ignoring an aggregate return, don't do anything.
+  if (atomics.getEvaluationKind() == TEK_Aggregate && resultSlot.isIgnored())
+    return RValue::getAggregate(0, false);
+
+  // The easiest way to do this this is to go through memory, but we
+  // try not to in some easy cases.
+  if (atomics.getEvaluationKind() == TEK_Scalar && !atomics.hasPadding()) {
+    llvm::Type *resultTy = CGM.getTypes().ConvertTypeForMem(valueType);
+    if (isa<llvm::IntegerType>(resultTy)) {
+      assert(result->getType() == resultTy);
+      result = EmitFromMemory(result, valueType);
+    } else if (isa<llvm::PointerType>(resultTy)) {
+      result = Builder.CreateIntToPtr(result, resultTy);
+    } else {
+      result = Builder.CreateBitCast(result, resultTy);
+    }
+    return RValue::get(result);
+  }
+
+  // Create a temporary.  This needs to be big enough to hold the
+  // atomic integer.
+  llvm::Value *temp;
+  bool tempIsVolatile = false;
+  CharUnits tempAlignment;
+  if (atomics.getEvaluationKind() == TEK_Aggregate &&
+      (!atomics.hasPadding() || resultSlot.isValueOfAtomic())) {
+    assert(!resultSlot.isIgnored());
+    if (resultSlot.isValueOfAtomic()) {
+      temp = resultSlot.getPaddedAtomicAddr();
+      tempAlignment = atomics.getAtomicAlignment();
+    } else {
+      temp = resultSlot.getAddr();
+      tempAlignment = atomics.getValueAlignment();
+    }
+    tempIsVolatile = resultSlot.isVolatile();
+  } else {
+    temp = CreateMemTemp(atomics.getAtomicType(), "atomic-load-temp");
+    tempAlignment = atomics.getAtomicAlignment();
+  }
+
+  // Slam the integer into the temporary.
+  llvm::Value *castTemp = atomics.emitCastToAtomicIntPointer(temp);
+  Builder.CreateAlignedStore(result, castTemp, tempAlignment.getQuantity())
+    ->setVolatile(tempIsVolatile);
+
+  return atomics.convertTempToRValue(temp, resultSlot);
+}
+
+
+
+/// 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, LValue dest) const {
+  // 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(dest.getAddress(),
+                          rvalue.getAggregateAddr(),
+                          getAtomicType(),
+                          (rvalue.isVolatileQualified()
+                           || dest.isVolatileQualified()),
+                          dest.getAlignment());
+    return;
+  }
+
+  // Okay, otherwise we're copying stuff.
+
+  // Zero out the buffer if necessary.
+  emitMemSetZeroIfNecessary(dest);
+
+  // Drill past the padding if present.
+  dest = projectValue(dest);
+
+  // Okay, store the rvalue in.
+  if (rvalue.isScalar()) {
+    CGF.EmitStoreOfScalar(rvalue.getScalarVal(), dest, /*init*/ true);
+  } else {
+    CGF.EmitStoreOfComplex(rvalue.getComplexVal(), dest, /*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());
+  emitCopyIntoMemory(rvalue, tempLV);
+  return temp;
+}
+
+/// 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,
+                                      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, dest);
+    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,
+                                                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;
+
+  // If we've got a scalar value of the right size, try to avoid going
+  // through memory.
+  if (rvalue.isScalar() && !atomics.hasPadding()) {
+    llvm::Value *value = rvalue.getScalarVal();
+    if (isa<llvm::IntegerType>(value->getType())) {
+      intValue = value;
+    } else {
+      llvm::IntegerType *inputIntTy =
+        llvm::IntegerType::get(getLLVMContext(), atomics.getValueSizeInBits());
+      if (isa<llvm::PointerType>(value->getType())) {
+        intValue = Builder.CreatePtrToInt(value, inputIntTy);
+      } else {
+        intValue = Builder.CreateBitCast(value, inputIntTy);
+      }
+    }
+
+  // Otherwise, we need to go through memory.
+  } else {
+    // Put the r-value in memory.
+    llvm::Value *addr = atomics.materializeRValue(rvalue);
+
+    // Cast the temporary to the atomic int type and pull a value out.
+    addr = atomics.emitCastToAtomicIntPointer(addr);
+    intValue = Builder.CreateAlignedLoad(addr,
+                                 atomics.getAtomicAlignment().getQuantity());
+  }
+
+  // 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(llvm::SequentiallyConsistent);
+
+  // Other decoration.
+  store->setAlignment(dest.getAlignment().getQuantity());
+  if (dest.isVolatileQualified())
+    store->setVolatile(true);
+  if (dest.getTBAAInfo())
+    CGM.DecorateInstruction(store, dest.getTBAAInfo());
+}
+
+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), dest);
+    return;
+  }
+
+  case TEK_Complex: {
+    ComplexPairTy value = EmitComplexExpr(init);
+    atomics.emitCopyIntoMemory(RValue::getComplex(value), dest);
+    return;
+  }
+
+  case TEK_Aggregate: {
+    // Memset the buffer first if there's any possibility of
+    // uninitialized internal bits.
+    atomics.emitMemSetZeroIfNecessary(dest);
+
+    // HACK: whether the initializer actually has an atomic type
+    // doesn't really seem reliable right now.
+    if (!init->getType()->isAtomicType()) {
+      dest = atomics.projectValue(dest);
+    }
+
+    // Evaluate the expression directly into the destination.
+    AggValueSlot slot = AggValueSlot::forLValue(dest,
+                                        AggValueSlot::IsNotDestructed,
+                                        AggValueSlot::DoesNotNeedGCBarriers,
+                                        AggValueSlot::IsNotAliased);
+    EmitAggExpr(init, slot);
+    return;
+  }
+  }
+  llvm_unreachable("bad evaluation kind");
+}