Merge branch 'master' of ssh://bitbucket.org/czan/honours

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diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
new file mode 100644
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--- /dev/null
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
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+//===------- ItaniumCXXABI.cpp - Emit LLVM Code from ASTs for a Module ----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This provides C++ code generation targeting the Itanium C++ ABI.  The class
+// in this file generates structures that follow the Itanium C++ ABI, which is
+// documented at:
+//  http://www.codesourcery.com/public/cxx-abi/abi.html
+//  http://www.codesourcery.com/public/cxx-abi/abi-eh.html
+//
+// It also supports the closely-related ARM ABI, documented at:
+// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0041c/IHI0041C_cppabi.pdf
+//
+//===----------------------------------------------------------------------===//
+
+#include "CGCXXABI.h"
+#include "CGRecordLayout.h"
+#include "CodeGenFunction.h"
+#include "CodeGenModule.h"
+#include <clang/AST/Mangle.h>
+#include <clang/AST/Type.h>
+#include <llvm/Intrinsics.h>
+#include <llvm/Target/TargetData.h>
+#include <llvm/Value.h>
+
+using namespace clang;
+using namespace CodeGen;
+
+namespace {
+class ItaniumCXXABI : public CodeGen::CGCXXABI {
+private:
+  llvm::IntegerType *PtrDiffTy;
+protected:
+  bool IsARM;
+
+  // It's a little silly for us to cache this.
+  llvm::IntegerType *getPtrDiffTy() {
+    if (!PtrDiffTy) {
+      QualType T = getContext().getPointerDiffType();
+      llvm::Type *Ty = CGM.getTypes().ConvertType(T);
+      PtrDiffTy = cast<llvm::IntegerType>(Ty);
+    }
+    return PtrDiffTy;
+  }
+
+  bool NeedsArrayCookie(const CXXNewExpr *expr);
+  bool NeedsArrayCookie(const CXXDeleteExpr *expr,
+                        QualType elementType);
+
+public:
+  ItaniumCXXABI(CodeGen::CodeGenModule &CGM, bool IsARM = false) :
+    CGCXXABI(CGM), PtrDiffTy(0), IsARM(IsARM) { }
+
+  bool isZeroInitializable(const MemberPointerType *MPT);
+
+  llvm::Type *ConvertMemberPointerType(const MemberPointerType *MPT);
+
+  llvm::Value *EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
+                                               llvm::Value *&This,
+                                               llvm::Value *MemFnPtr,
+                                               const MemberPointerType *MPT);
+
+  llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF,
+                                            llvm::Value *Base,
+                                            llvm::Value *MemPtr,
+                                            const MemberPointerType *MPT);
+
+  llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
+                                           const CastExpr *E,
+                                           llvm::Value *Src);
+  llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
+                                              llvm::Constant *Src);
+
+  llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
+
+  llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD);
+  llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
+                                        CharUnits offset);
+  llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT);
+  llvm::Constant *BuildMemberPointer(const CXXMethodDecl *MD,
+                                     CharUnits ThisAdjustment);
+
+  llvm::Value *EmitMemberPointerComparison(CodeGenFunction &CGF,
+                                           llvm::Value *L,
+                                           llvm::Value *R,
+                                           const MemberPointerType *MPT,
+                                           bool Inequality);
+
+  llvm::Value *EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
+                                          llvm::Value *Addr,
+                                          const MemberPointerType *MPT);
+
+  void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
+                                 CXXCtorType T,
+                                 CanQualType &ResTy,
+                                 SmallVectorImpl<CanQualType> &ArgTys);
+
+  void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
+                                CXXDtorType T,
+                                CanQualType &ResTy,
+                                SmallVectorImpl<CanQualType> &ArgTys);
+
+  void BuildInstanceFunctionParams(CodeGenFunction &CGF,
+                                   QualType &ResTy,
+                                   FunctionArgList &Params);
+
+  void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
+
+  CharUnits GetArrayCookieSize(const CXXNewExpr *expr);
+  llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
+                                     llvm::Value *NewPtr,
+                                     llvm::Value *NumElements,
+                                     const CXXNewExpr *expr,
+                                     QualType ElementType);
+  void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr,
+                       const CXXDeleteExpr *expr,
+                       QualType ElementType, llvm::Value *&NumElements,
+                       llvm::Value *&AllocPtr, CharUnits &CookieSize);
+
+  void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
+                       llvm::GlobalVariable *DeclPtr, bool PerformInit);
+};
+
+class ARMCXXABI : public ItaniumCXXABI {
+public:
+  ARMCXXABI(CodeGen::CodeGenModule &CGM) : ItaniumCXXABI(CGM, /*ARM*/ true) {}
+
+  void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
+                                 CXXCtorType T,
+                                 CanQualType &ResTy,
+                                 SmallVectorImpl<CanQualType> &ArgTys);
+
+  void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
+                                CXXDtorType T,
+                                CanQualType &ResTy,
+                                SmallVectorImpl<CanQualType> &ArgTys);
+
+  void BuildInstanceFunctionParams(CodeGenFunction &CGF,
+                                   QualType &ResTy,
+                                   FunctionArgList &Params);
+
+  void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
+
+  void EmitReturnFromThunk(CodeGenFunction &CGF, RValue RV, QualType ResTy);
+
+  CharUnits GetArrayCookieSize(const CXXNewExpr *expr);
+  llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
+                                     llvm::Value *NewPtr,
+                                     llvm::Value *NumElements,
+                                     const CXXNewExpr *expr,
+                                     QualType ElementType);
+  void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr,
+                       const CXXDeleteExpr *expr,
+                       QualType ElementType, llvm::Value *&NumElements,
+                       llvm::Value *&AllocPtr, CharUnits &CookieSize);
+
+private:
+  /// \brief Returns true if the given instance method is one of the
+  /// kinds that the ARM ABI says returns 'this'.
+  static bool HasThisReturn(GlobalDecl GD) {
+    const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
+    return ((isa<CXXDestructorDecl>(MD) && GD.getDtorType() != Dtor_Deleting) ||
+            (isa<CXXConstructorDecl>(MD)));
+  }
+};
+}
+
+CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) {
+  return new ItaniumCXXABI(CGM);
+}
+
+CodeGen::CGCXXABI *CodeGen::CreateARMCXXABI(CodeGenModule &CGM) {
+  return new ARMCXXABI(CGM);
+}
+
+llvm::Type *
+ItaniumCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
+  if (MPT->isMemberDataPointer())
+    return getPtrDiffTy();
+  return llvm::StructType::get(getPtrDiffTy(), getPtrDiffTy(), NULL);
+}
+
+/// In the Itanium and ARM ABIs, method pointers have the form:
+///   struct { ptrdiff_t ptr; ptrdiff_t adj; } memptr;
+///
+/// In the Itanium ABI:
+///  - method pointers are virtual if (memptr.ptr & 1) is nonzero
+///  - the this-adjustment is (memptr.adj)
+///  - the virtual offset is (memptr.ptr - 1)
+///
+/// In the ARM ABI:
+///  - method pointers are virtual if (memptr.adj & 1) is nonzero
+///  - the this-adjustment is (memptr.adj >> 1)
+///  - the virtual offset is (memptr.ptr)
+/// ARM uses 'adj' for the virtual flag because Thumb functions
+/// may be only single-byte aligned.
+///
+/// If the member is virtual, the adjusted 'this' pointer points
+/// to a vtable pointer from which the virtual offset is applied.
+///
+/// If the member is non-virtual, memptr.ptr is the address of
+/// the function to call.
+llvm::Value *
+ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
+                                               llvm::Value *&This,
+                                               llvm::Value *MemFnPtr,
+                                               const MemberPointerType *MPT) {
+  CGBuilderTy &Builder = CGF.Builder;
+
+  const FunctionProtoType *FPT = 
+    MPT->getPointeeType()->getAs<FunctionProtoType>();
+  const CXXRecordDecl *RD = 
+    cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl());
+
+  llvm::FunctionType *FTy = 
+    CGM.getTypes().GetFunctionType(
+      CGM.getTypes().arrangeCXXMethodType(RD, FPT));
+
+  llvm::IntegerType *ptrdiff = getPtrDiffTy();
+  llvm::Constant *ptrdiff_1 = llvm::ConstantInt::get(ptrdiff, 1);
+
+  llvm::BasicBlock *FnVirtual = CGF.createBasicBlock("memptr.virtual");
+  llvm::BasicBlock *FnNonVirtual = CGF.createBasicBlock("memptr.nonvirtual");
+  llvm::BasicBlock *FnEnd = CGF.createBasicBlock("memptr.end");
+
+  // Extract memptr.adj, which is in the second field.
+  llvm::Value *RawAdj = Builder.CreateExtractValue(MemFnPtr, 1, "memptr.adj");
+
+  // Compute the true adjustment.
+  llvm::Value *Adj = RawAdj;
+  if (IsARM)
+    Adj = Builder.CreateAShr(Adj, ptrdiff_1, "memptr.adj.shifted");
+
+  // Apply the adjustment and cast back to the original struct type
+  // for consistency.
+  llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy());
+  Ptr = Builder.CreateInBoundsGEP(Ptr, Adj);
+  This = Builder.CreateBitCast(Ptr, This->getType(), "this.adjusted");
+  
+  // Load the function pointer.
+  llvm::Value *FnAsInt = Builder.CreateExtractValue(MemFnPtr, 0, "memptr.ptr");
+  
+  // If the LSB in the function pointer is 1, the function pointer points to
+  // a virtual function.
+  llvm::Value *IsVirtual;
+  if (IsARM)
+    IsVirtual = Builder.CreateAnd(RawAdj, ptrdiff_1);
+  else
+    IsVirtual = Builder.CreateAnd(FnAsInt, ptrdiff_1);
+  IsVirtual = Builder.CreateIsNotNull(IsVirtual, "memptr.isvirtual");
+  Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual);
+
+  // In the virtual path, the adjustment left 'This' pointing to the
+  // vtable of the correct base subobject.  The "function pointer" is an
+  // offset within the vtable (+1 for the virtual flag on non-ARM).
+  CGF.EmitBlock(FnVirtual);
+
+  // Cast the adjusted this to a pointer to vtable pointer and load.
+  llvm::Type *VTableTy = Builder.getInt8PtrTy();
+  llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy->getPointerTo());
+  VTable = Builder.CreateLoad(VTable, "memptr.vtable");
+
+  // Apply the offset.
+  llvm::Value *VTableOffset = FnAsInt;
+  if (!IsARM) VTableOffset = Builder.CreateSub(VTableOffset, ptrdiff_1);
+  VTable = Builder.CreateGEP(VTable, VTableOffset);
+
+  // Load the virtual function to call.
+  VTable = Builder.CreateBitCast(VTable, FTy->getPointerTo()->getPointerTo());
+  llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "memptr.virtualfn");
+  CGF.EmitBranch(FnEnd);
+
+  // In the non-virtual path, the function pointer is actually a
+  // function pointer.
+  CGF.EmitBlock(FnNonVirtual);
+  llvm::Value *NonVirtualFn =
+    Builder.CreateIntToPtr(FnAsInt, FTy->getPointerTo(), "memptr.nonvirtualfn");
+  
+  // We're done.
+  CGF.EmitBlock(FnEnd);
+  llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo(), 2);
+  Callee->addIncoming(VirtualFn, FnVirtual);
+  Callee->addIncoming(NonVirtualFn, FnNonVirtual);
+  return Callee;
+}
+
+/// Compute an l-value by applying the given pointer-to-member to a
+/// base object.
+llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF,
+                                                         llvm::Value *Base,
+                                                         llvm::Value *MemPtr,
+                                           const MemberPointerType *MPT) {
+  assert(MemPtr->getType() == getPtrDiffTy());
+
+  CGBuilderTy &Builder = CGF.Builder;
+
+  unsigned AS = cast<llvm::PointerType>(Base->getType())->getAddressSpace();
+
+  // Cast to char*.
+  Base = Builder.CreateBitCast(Base, Builder.getInt8Ty()->getPointerTo(AS));
+
+  // Apply the offset, which we assume is non-null.
+  llvm::Value *Addr = Builder.CreateInBoundsGEP(Base, MemPtr, "memptr.offset");
+
+  // Cast the address to the appropriate pointer type, adopting the
+  // address space of the base pointer.
+  llvm::Type *PType
+    = CGF.ConvertTypeForMem(MPT->getPointeeType())->getPointerTo(AS);
+  return Builder.CreateBitCast(Addr, PType);
+}
+
+/// Perform a bitcast, derived-to-base, or base-to-derived member pointer
+/// conversion.
+///
+/// Bitcast conversions are always a no-op under Itanium.
+///
+/// Obligatory offset/adjustment diagram:
+///         <-- offset -->          <-- adjustment -->
+///   |--------------------------|----------------------|--------------------|
+///   ^Derived address point     ^Base address point    ^Member address point
+///
+/// So when converting a base member pointer to a derived member pointer,
+/// we add the offset to the adjustment because the address point has
+/// decreased;  and conversely, when converting a derived MP to a base MP
+/// we subtract the offset from the adjustment because the address point
+/// has increased.
+///
+/// The standard forbids (at compile time) conversion to and from
+/// virtual bases, which is why we don't have to consider them here.
+///
+/// The standard forbids (at run time) casting a derived MP to a base
+/// MP when the derived MP does not point to a member of the base.
+/// This is why -1 is a reasonable choice for null data member
+/// pointers.
+llvm::Value *
+ItaniumCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
+                                           const CastExpr *E,
+                                           llvm::Value *src) {
+  assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
+         E->getCastKind() == CK_BaseToDerivedMemberPointer ||
+         E->getCastKind() == CK_ReinterpretMemberPointer);
+
+  // Under Itanium, reinterprets don't require any additional processing.
+  if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
+
+  // Use constant emission if we can.
+  if (isa<llvm::Constant>(src))
+    return EmitMemberPointerConversion(E, cast<llvm::Constant>(src));
+
+  llvm::Constant *adj = getMemberPointerAdjustment(E);
+  if (!adj) return src;
+
+  CGBuilderTy &Builder = CGF.Builder;
+  bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
+
+  const MemberPointerType *destTy =
+    E->getType()->castAs<MemberPointerType>();
+
+  // For member data pointers, this is just a matter of adding the
+  // offset if the source is non-null.
+  if (destTy->isMemberDataPointer()) {
+    llvm::Value *dst;
+    if (isDerivedToBase)
+      dst = Builder.CreateNSWSub(src, adj, "adj");
+    else
+      dst = Builder.CreateNSWAdd(src, adj, "adj");
+
+    // Null check.
+    llvm::Value *null = llvm::Constant::getAllOnesValue(src->getType());
+    llvm::Value *isNull = Builder.CreateICmpEQ(src, null, "memptr.isnull");
+    return Builder.CreateSelect(isNull, src, dst);
+  }
+
+  // The this-adjustment is left-shifted by 1 on ARM.
+  if (IsARM) {
+    uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
+    offset <<= 1;
+    adj = llvm::ConstantInt::get(adj->getType(), offset);
+  }
+
+  llvm::Value *srcAdj = Builder.CreateExtractValue(src, 1, "src.adj");
+  llvm::Value *dstAdj;
+  if (isDerivedToBase)
+    dstAdj = Builder.CreateNSWSub(srcAdj, adj, "adj");
+  else
+    dstAdj = Builder.CreateNSWAdd(srcAdj, adj, "adj");
+
+  return Builder.CreateInsertValue(src, dstAdj, 1);
+}
+
+llvm::Constant *
+ItaniumCXXABI::EmitMemberPointerConversion(const CastExpr *E,
+                                           llvm::Constant *src) {
+  assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
+         E->getCastKind() == CK_BaseToDerivedMemberPointer ||
+         E->getCastKind() == CK_ReinterpretMemberPointer);
+
+  // Under Itanium, reinterprets don't require any additional processing.
+  if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
+
+  // If the adjustment is trivial, we don't need to do anything.
+  llvm::Constant *adj = getMemberPointerAdjustment(E);
+  if (!adj) return src;
+
+  bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
+
+  const MemberPointerType *destTy =
+    E->getType()->castAs<MemberPointerType>();
+
+  // For member data pointers, this is just a matter of adding the
+  // offset if the source is non-null.
+  if (destTy->isMemberDataPointer()) {
+    // null maps to null.
+    if (src->isAllOnesValue()) return src;
+
+    if (isDerivedToBase)
+      return llvm::ConstantExpr::getNSWSub(src, adj);
+    else
+      return llvm::ConstantExpr::getNSWAdd(src, adj);
+  }
+
+  // The this-adjustment is left-shifted by 1 on ARM.
+  if (IsARM) {
+    uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
+    offset <<= 1;
+    adj = llvm::ConstantInt::get(adj->getType(), offset);
+  }
+
+  llvm::Constant *srcAdj = llvm::ConstantExpr::getExtractValue(src, 1);
+  llvm::Constant *dstAdj;
+  if (isDerivedToBase)
+    dstAdj = llvm::ConstantExpr::getNSWSub(srcAdj, adj);
+  else
+    dstAdj = llvm::ConstantExpr::getNSWAdd(srcAdj, adj);
+
+  return llvm::ConstantExpr::getInsertValue(src, dstAdj, 1);
+}
+
+llvm::Constant *
+ItaniumCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
+  llvm::Type *ptrdiff_t = getPtrDiffTy();
+
+  // Itanium C++ ABI 2.3:
+  //   A NULL pointer is represented as -1.
+  if (MPT->isMemberDataPointer()) 
+    return llvm::ConstantInt::get(ptrdiff_t, -1ULL, /*isSigned=*/true);
+
+  llvm::Constant *Zero = llvm::ConstantInt::get(ptrdiff_t, 0);
+  llvm::Constant *Values[2] = { Zero, Zero };
+  return llvm::ConstantStruct::getAnon(Values);
+}
+
+llvm::Constant *
+ItaniumCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
+                                     CharUnits offset) {
+  // Itanium C++ ABI 2.3:
+  //   A pointer to data member is an offset from the base address of
+  //   the class object containing it, represented as a ptrdiff_t
+  return llvm::ConstantInt::get(getPtrDiffTy(), offset.getQuantity());
+}
+
+llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const CXXMethodDecl *MD) {
+  return BuildMemberPointer(MD, CharUnits::Zero());
+}
+
+llvm::Constant *ItaniumCXXABI::BuildMemberPointer(const CXXMethodDecl *MD,
+                                                  CharUnits ThisAdjustment) {
+  assert(MD->isInstance() && "Member function must not be static!");
+  MD = MD->getCanonicalDecl();
+
+  CodeGenTypes &Types = CGM.getTypes();
+  llvm::Type *ptrdiff_t = getPtrDiffTy();
+
+  // Get the function pointer (or index if this is a virtual function).
+  llvm::Constant *MemPtr[2];
+  if (MD->isVirtual()) {
+    uint64_t Index = CGM.getVTableContext().getMethodVTableIndex(MD);
+
+    const ASTContext &Context = getContext();
+    CharUnits PointerWidth =
+      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
+    uint64_t VTableOffset = (Index * PointerWidth.getQuantity());
+
+    if (IsARM) {
+      // ARM C++ ABI 3.2.1:
+      //   This ABI specifies that adj contains twice the this
+      //   adjustment, plus 1 if the member function is virtual. The
+      //   least significant bit of adj then makes exactly the same
+      //   discrimination as the least significant bit of ptr does for
+      //   Itanium.
+      MemPtr[0] = llvm::ConstantInt::get(ptrdiff_t, VTableOffset);
+      MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t,
+                                         2 * ThisAdjustment.getQuantity() + 1);
+    } else {
+      // Itanium C++ ABI 2.3:
+      //   For a virtual function, [the pointer field] is 1 plus the
+      //   virtual table offset (in bytes) of the function,
+      //   represented as a ptrdiff_t.
+      MemPtr[0] = llvm::ConstantInt::get(ptrdiff_t, VTableOffset + 1);
+      MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t,
+                                         ThisAdjustment.getQuantity());
+    }
+  } else {
+    const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
+    llvm::Type *Ty;
+    // Check whether the function has a computable LLVM signature.
+    if (Types.isFuncTypeConvertible(FPT)) {
+      // The function has a computable LLVM signature; use the correct type.
+      Ty = Types.GetFunctionType(Types.arrangeCXXMethodDeclaration(MD));
+    } else {
+      // Use an arbitrary non-function type to tell GetAddrOfFunction that the
+      // function type is incomplete.
+      Ty = ptrdiff_t;
+    }
+    llvm::Constant *addr = CGM.GetAddrOfFunction(MD, Ty);
+
+    MemPtr[0] = llvm::ConstantExpr::getPtrToInt(addr, ptrdiff_t);
+    MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t, (IsARM ? 2 : 1) *
+                                       ThisAdjustment.getQuantity());
+  }
+  
+  return llvm::ConstantStruct::getAnon(MemPtr);
+}
+
+llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const APValue &MP,
+                                                 QualType MPType) {
+  const MemberPointerType *MPT = MPType->castAs<MemberPointerType>();
+  const ValueDecl *MPD = MP.getMemberPointerDecl();
+  if (!MPD)
+    return EmitNullMemberPointer(MPT);
+
+  // Compute the this-adjustment.
+  CharUnits ThisAdjustment = CharUnits::Zero();
+  ArrayRef<const CXXRecordDecl*> Path = MP.getMemberPointerPath();
+  bool DerivedMember = MP.isMemberPointerToDerivedMember();
+  const CXXRecordDecl *RD = cast<CXXRecordDecl>(MPD->getDeclContext());
+  for (unsigned I = 0, N = Path.size(); I != N; ++I) {
+    const CXXRecordDecl *Base = RD;
+    const CXXRecordDecl *Derived = Path[I];
+    if (DerivedMember)
+      std::swap(Base, Derived);
+    ThisAdjustment +=
+      getContext().getASTRecordLayout(Derived).getBaseClassOffset(Base);
+    RD = Path[I];
+  }
+  if (DerivedMember)
+    ThisAdjustment = -ThisAdjustment;
+
+  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(MPD))
+    return BuildMemberPointer(MD, ThisAdjustment);
+
+  CharUnits FieldOffset =
+    getContext().toCharUnitsFromBits(getContext().getFieldOffset(MPD));
+  return EmitMemberDataPointer(MPT, ThisAdjustment + FieldOffset);
+}
+
+/// The comparison algorithm is pretty easy: the member pointers are
+/// the same if they're either bitwise identical *or* both null.
+///
+/// ARM is different here only because null-ness is more complicated.
+llvm::Value *
+ItaniumCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
+                                           llvm::Value *L,
+                                           llvm::Value *R,
+                                           const MemberPointerType *MPT,
+                                           bool Inequality) {
+  CGBuilderTy &Builder = CGF.Builder;
+
+  llvm::ICmpInst::Predicate Eq;
+  llvm::Instruction::BinaryOps And, Or;
+  if (Inequality) {
+    Eq = llvm::ICmpInst::ICMP_NE;
+    And = llvm::Instruction::Or;
+    Or = llvm::Instruction::And;
+  } else {
+    Eq = llvm::ICmpInst::ICMP_EQ;
+    And = llvm::Instruction::And;
+    Or = llvm::Instruction::Or;
+  }
+
+  // Member data pointers are easy because there's a unique null
+  // value, so it just comes down to bitwise equality.
+  if (MPT->isMemberDataPointer())
+    return Builder.CreateICmp(Eq, L, R);
+
+  // For member function pointers, the tautologies are more complex.
+  // The Itanium tautology is:
+  //   (L == R) <==> (L.ptr == R.ptr && (L.ptr == 0 || L.adj == R.adj))
+  // The ARM tautology is:
+  //   (L == R) <==> (L.ptr == R.ptr &&
+  //                  (L.adj == R.adj ||
+  //                   (L.ptr == 0 && ((L.adj|R.adj) & 1) == 0)))
+  // The inequality tautologies have exactly the same structure, except
+  // applying De Morgan's laws.
+  
+  llvm::Value *LPtr = Builder.CreateExtractValue(L, 0, "lhs.memptr.ptr");
+  llvm::Value *RPtr = Builder.CreateExtractValue(R, 0, "rhs.memptr.ptr");
+
+  // This condition tests whether L.ptr == R.ptr.  This must always be
+  // true for equality to hold.
+  llvm::Value *PtrEq = Builder.CreateICmp(Eq, LPtr, RPtr, "cmp.ptr");
+
+  // This condition, together with the assumption that L.ptr == R.ptr,
+  // tests whether the pointers are both null.  ARM imposes an extra
+  // condition.
+  llvm::Value *Zero = llvm::Constant::getNullValue(LPtr->getType());
+  llvm::Value *EqZero = Builder.CreateICmp(Eq, LPtr, Zero, "cmp.ptr.null");
+
+  // This condition tests whether L.adj == R.adj.  If this isn't
+  // true, the pointers are unequal unless they're both null.
+  llvm::Value *LAdj = Builder.CreateExtractValue(L, 1, "lhs.memptr.adj");
+  llvm::Value *RAdj = Builder.CreateExtractValue(R, 1, "rhs.memptr.adj");
+  llvm::Value *AdjEq = Builder.CreateICmp(Eq, LAdj, RAdj, "cmp.adj");
+
+  // Null member function pointers on ARM clear the low bit of Adj,
+  // so the zero condition has to check that neither low bit is set.
+  if (IsARM) {
+    llvm::Value *One = llvm::ConstantInt::get(LPtr->getType(), 1);
+
+    // Compute (l.adj | r.adj) & 1 and test it against zero.
+    llvm::Value *OrAdj = Builder.CreateOr(LAdj, RAdj, "or.adj");
+    llvm::Value *OrAdjAnd1 = Builder.CreateAnd(OrAdj, One);
+    llvm::Value *OrAdjAnd1EqZero = Builder.CreateICmp(Eq, OrAdjAnd1, Zero,
+                                                      "cmp.or.adj");
+    EqZero = Builder.CreateBinOp(And, EqZero, OrAdjAnd1EqZero);
+  }
+
+  // Tie together all our conditions.
+  llvm::Value *Result = Builder.CreateBinOp(Or, EqZero, AdjEq);
+  Result = Builder.CreateBinOp(And, PtrEq, Result,
+                               Inequality ? "memptr.ne" : "memptr.eq");
+  return Result;
+}
+
+llvm::Value *
+ItaniumCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
+                                          llvm::Value *MemPtr,
+                                          const MemberPointerType *MPT) {
+  CGBuilderTy &Builder = CGF.Builder;
+
+  /// For member data pointers, this is just a check against -1.
+  if (MPT->isMemberDataPointer()) {
+    assert(MemPtr->getType() == getPtrDiffTy());
+    llvm::Value *NegativeOne =
+      llvm::Constant::getAllOnesValue(MemPtr->getType());
+    return Builder.CreateICmpNE(MemPtr, NegativeOne, "memptr.tobool");
+  }
+  
+  // In Itanium, a member function pointer is not null if 'ptr' is not null.
+  llvm::Value *Ptr = Builder.CreateExtractValue(MemPtr, 0, "memptr.ptr");
+
+  llvm::Constant *Zero = llvm::ConstantInt::get(Ptr->getType(), 0);
+  llvm::Value *Result = Builder.CreateICmpNE(Ptr, Zero, "memptr.tobool");
+
+  // On ARM, a member function pointer is also non-null if the low bit of 'adj'
+  // (the virtual bit) is set.
+  if (IsARM) {
+    llvm::Constant *One = llvm::ConstantInt::get(Ptr->getType(), 1);
+    llvm::Value *Adj = Builder.CreateExtractValue(MemPtr, 1, "memptr.adj");
+    llvm::Value *VirtualBit = Builder.CreateAnd(Adj, One, "memptr.virtualbit");
+    llvm::Value *IsVirtual = Builder.CreateICmpNE(VirtualBit, Zero,
+                                                  "memptr.isvirtual");
+    Result = Builder.CreateOr(Result, IsVirtual);
+  }
+
+  return Result;
+}
+
+/// The Itanium ABI requires non-zero initialization only for data
+/// member pointers, for which '0' is a valid offset.
+bool ItaniumCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
+  return MPT->getPointeeType()->isFunctionType();
+}
+
+/// The generic ABI passes 'this', plus a VTT if it's initializing a
+/// base subobject.
+void ItaniumCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
+                                              CXXCtorType Type,
+                                              CanQualType &ResTy,
+                                SmallVectorImpl<CanQualType> &ArgTys) {
+  ASTContext &Context = getContext();
+
+  // 'this' is already there.
+
+  // Check if we need to add a VTT parameter (which has type void **).
+  if (Type == Ctor_Base && Ctor->getParent()->getNumVBases() != 0)
+    ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
+}
+
+/// The ARM ABI does the same as the Itanium ABI, but returns 'this'.
+void ARMCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
+                                          CXXCtorType Type,
+                                          CanQualType &ResTy,
+                                SmallVectorImpl<CanQualType> &ArgTys) {
+  ItaniumCXXABI::BuildConstructorSignature(Ctor, Type, ResTy, ArgTys);
+  ResTy = ArgTys[0];
+}
+
+/// The generic ABI passes 'this', plus a VTT if it's destroying a
+/// base subobject.
+void ItaniumCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
+                                             CXXDtorType Type,
+                                             CanQualType &ResTy,
+                                SmallVectorImpl<CanQualType> &ArgTys) {
+  ASTContext &Context = getContext();
+
+  // 'this' is already there.
+
+  // Check if we need to add a VTT parameter (which has type void **).
+  if (Type == Dtor_Base && Dtor->getParent()->getNumVBases() != 0)
+    ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
+}
+
+/// The ARM ABI does the same as the Itanium ABI, but returns 'this'
+/// for non-deleting destructors.
+void ARMCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
+                                         CXXDtorType Type,
+                                         CanQualType &ResTy,
+                                SmallVectorImpl<CanQualType> &ArgTys) {
+  ItaniumCXXABI::BuildDestructorSignature(Dtor, Type, ResTy, ArgTys);
+
+  if (Type != Dtor_Deleting)
+    ResTy = ArgTys[0];
+}
+
+void ItaniumCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
+                                                QualType &ResTy,
+                                                FunctionArgList &Params) {
+  /// Create the 'this' variable.
+  BuildThisParam(CGF, Params);
+
+  const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
+  assert(MD->isInstance());
+
+  // Check if we need a VTT parameter as well.
+  if (CodeGenVTables::needsVTTParameter(CGF.CurGD)) {
+    ASTContext &Context = getContext();
+
+    // FIXME: avoid the fake decl
+    QualType T = Context.getPointerType(Context.VoidPtrTy);
+    ImplicitParamDecl *VTTDecl
+      = ImplicitParamDecl::Create(Context, 0, MD->getLocation(),
+                                  &Context.Idents.get("vtt"), T);
+    Params.push_back(VTTDecl);
+    getVTTDecl(CGF) = VTTDecl;
+  }
+}
+
+void ARMCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
+                                            QualType &ResTy,
+                                            FunctionArgList &Params) {
+  ItaniumCXXABI::BuildInstanceFunctionParams(CGF, ResTy, Params);
+
+  // Return 'this' from certain constructors and destructors.
+  if (HasThisReturn(CGF.CurGD))
+    ResTy = Params[0]->getType();
+}
+
+void ItaniumCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
+  /// Initialize the 'this' slot.
+  EmitThisParam(CGF);
+
+  /// Initialize the 'vtt' slot if needed.
+  if (getVTTDecl(CGF)) {
+    getVTTValue(CGF)
+      = CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getVTTDecl(CGF)),
+                               "vtt");
+  }
+}
+
+void ARMCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
+  ItaniumCXXABI::EmitInstanceFunctionProlog(CGF);
+
+  /// Initialize the return slot to 'this' at the start of the
+  /// function.
+  if (HasThisReturn(CGF.CurGD))
+    CGF.Builder.CreateStore(getThisValue(CGF), CGF.ReturnValue);
+}
+
+void ARMCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
+                                    RValue RV, QualType ResultType) {
+  if (!isa<CXXDestructorDecl>(CGF.CurGD.getDecl()))
+    return ItaniumCXXABI::EmitReturnFromThunk(CGF, RV, ResultType);
+
+  // Destructor thunks in the ARM ABI have indeterminate results.
+  llvm::Type *T =
+    cast<llvm::PointerType>(CGF.ReturnValue->getType())->getElementType();
+  RValue Undef = RValue::get(llvm::UndefValue::get(T));
+  return ItaniumCXXABI::EmitReturnFromThunk(CGF, Undef, ResultType);
+}
+
+/************************** Array allocation cookies **************************/
+
+bool ItaniumCXXABI::NeedsArrayCookie(const CXXNewExpr *expr) {
+  // If the class's usual deallocation function takes two arguments,
+  // it needs a cookie.
+  if (expr->doesUsualArrayDeleteWantSize())
+    return true;
+
+  // Automatic Reference Counting:
+  //   We need an array cookie for pointers with strong or weak lifetime.
+  QualType AllocatedType = expr->getAllocatedType();
+  if (getContext().getLangOpts().ObjCAutoRefCount &&
+      AllocatedType->isObjCLifetimeType()) {
+    switch (AllocatedType.getObjCLifetime()) {
+    case Qualifiers::OCL_None:
+    case Qualifiers::OCL_ExplicitNone:
+    case Qualifiers::OCL_Autoreleasing:
+      return false;
+      
+    case Qualifiers::OCL_Strong:
+    case Qualifiers::OCL_Weak:
+      return true;
+    }
+  }
+
+  // Otherwise, if the class has a non-trivial destructor, it always
+  // needs a cookie.
+  const CXXRecordDecl *record =
+    AllocatedType->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
+  return (record && !record->hasTrivialDestructor());
+}
+
+bool ItaniumCXXABI::NeedsArrayCookie(const CXXDeleteExpr *expr,
+                                     QualType elementType) {
+  // If the class's usual deallocation function takes two arguments,
+  // it needs a cookie.
+  if (expr->doesUsualArrayDeleteWantSize())
+    return true;
+
+  return elementType.isDestructedType();
+}
+
+CharUnits ItaniumCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) {
+  if (!NeedsArrayCookie(expr))
+    return CharUnits::Zero();
+  
+  // Padding is the maximum of sizeof(size_t) and alignof(elementType)
+  ASTContext &Ctx = getContext();
+  return std::max(Ctx.getTypeSizeInChars(Ctx.getSizeType()),
+                  Ctx.getTypeAlignInChars(expr->getAllocatedType()));
+}
+
+llvm::Value *ItaniumCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
+                                                  llvm::Value *NewPtr,
+                                                  llvm::Value *NumElements,
+                                                  const CXXNewExpr *expr,
+                                                  QualType ElementType) {
+  assert(NeedsArrayCookie(expr));
+
+  unsigned AS = cast<llvm::PointerType>(NewPtr->getType())->getAddressSpace();
+
+  ASTContext &Ctx = getContext();
+  QualType SizeTy = Ctx.getSizeType();
+  CharUnits SizeSize = Ctx.getTypeSizeInChars(SizeTy);
+
+  // The size of the cookie.
+  CharUnits CookieSize =
+    std::max(SizeSize, Ctx.getTypeAlignInChars(ElementType));
+
+  // Compute an offset to the cookie.
+  llvm::Value *CookiePtr = NewPtr;
+  CharUnits CookieOffset = CookieSize - SizeSize;
+  if (!CookieOffset.isZero())
+    CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_64(CookiePtr,
+                                                 CookieOffset.getQuantity());
+
+  // Write the number of elements into the appropriate slot.
+  llvm::Value *NumElementsPtr
+    = CGF.Builder.CreateBitCast(CookiePtr,
+                                CGF.ConvertType(SizeTy)->getPointerTo(AS));
+  CGF.Builder.CreateStore(NumElements, NumElementsPtr);
+
+  // Finally, compute a pointer to the actual data buffer by skipping
+  // over the cookie completely.
+  return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr,
+                                                CookieSize.getQuantity());  
+}
+
+void ItaniumCXXABI::ReadArrayCookie(CodeGenFunction &CGF,
+                                    llvm::Value *Ptr,
+                                    const CXXDeleteExpr *expr,
+                                    QualType ElementType,
+                                    llvm::Value *&NumElements,
+                                    llvm::Value *&AllocPtr,
+                                    CharUnits &CookieSize) {
+  // Derive a char* in the same address space as the pointer.
+  unsigned AS = cast<llvm::PointerType>(Ptr->getType())->getAddressSpace();
+  llvm::Type *CharPtrTy = CGF.Builder.getInt8Ty()->getPointerTo(AS);
+
+  // If we don't need an array cookie, bail out early.
+  if (!NeedsArrayCookie(expr, ElementType)) {
+    AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy);
+    NumElements = 0;
+    CookieSize = CharUnits::Zero();
+    return;
+  }
+
+  QualType SizeTy = getContext().getSizeType();
+  CharUnits SizeSize = getContext().getTypeSizeInChars(SizeTy);
+  llvm::Type *SizeLTy = CGF.ConvertType(SizeTy);
+  
+  CookieSize
+    = std::max(SizeSize, getContext().getTypeAlignInChars(ElementType));
+
+  CharUnits NumElementsOffset = CookieSize - SizeSize;
+
+  // Compute the allocated pointer.
+  AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy);
+  AllocPtr = CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr,
+                                                    -CookieSize.getQuantity());
+
+  llvm::Value *NumElementsPtr = AllocPtr;
+  if (!NumElementsOffset.isZero())
+    NumElementsPtr =
+      CGF.Builder.CreateConstInBoundsGEP1_64(NumElementsPtr,
+                                             NumElementsOffset.getQuantity());
+  NumElementsPtr = 
+    CGF.Builder.CreateBitCast(NumElementsPtr, SizeLTy->getPointerTo(AS));
+  NumElements = CGF.Builder.CreateLoad(NumElementsPtr);
+}
+
+CharUnits ARMCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) {
+  if (!NeedsArrayCookie(expr))
+    return CharUnits::Zero();
+
+  // On ARM, the cookie is always:
+  //   struct array_cookie {
+  //     std::size_t element_size; // element_size != 0
+  //     std::size_t element_count;
+  //   };
+  // TODO: what should we do if the allocated type actually wants
+  // greater alignment?
+  return getContext().getTypeSizeInChars(getContext().getSizeType()) * 2;
+}
+
+llvm::Value *ARMCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
+                                              llvm::Value *NewPtr,
+                                              llvm::Value *NumElements,
+                                              const CXXNewExpr *expr,
+                                              QualType ElementType) {
+  assert(NeedsArrayCookie(expr));
+
+  // NewPtr is a char*.
+
+  unsigned AS = cast<llvm::PointerType>(NewPtr->getType())->getAddressSpace();
+
+  ASTContext &Ctx = getContext();
+  CharUnits SizeSize = Ctx.getTypeSizeInChars(Ctx.getSizeType());
+  llvm::IntegerType *SizeTy =
+    cast<llvm::IntegerType>(CGF.ConvertType(Ctx.getSizeType()));
+
+  // The cookie is always at the start of the buffer.
+  llvm::Value *CookiePtr = NewPtr;
+
+  // The first element is the element size.
+  CookiePtr = CGF.Builder.CreateBitCast(CookiePtr, SizeTy->getPointerTo(AS));
+  llvm::Value *ElementSize = llvm::ConstantInt::get(SizeTy,
+                          Ctx.getTypeSizeInChars(ElementType).getQuantity());
+  CGF.Builder.CreateStore(ElementSize, CookiePtr);
+
+  // The second element is the element count.
+  CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_32(CookiePtr, 1);
+  CGF.Builder.CreateStore(NumElements, CookiePtr);
+
+  // Finally, compute a pointer to the actual data buffer by skipping
+  // over the cookie completely.
+  CharUnits CookieSize = 2 * SizeSize;
+  return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr,
+                                                CookieSize.getQuantity());
+}
+
+void ARMCXXABI::ReadArrayCookie(CodeGenFunction &CGF,
+                                llvm::Value *Ptr,
+                                const CXXDeleteExpr *expr,
+                                QualType ElementType,
+                                llvm::Value *&NumElements,
+                                llvm::Value *&AllocPtr,
+                                CharUnits &CookieSize) {
+  // Derive a char* in the same address space as the pointer.
+  unsigned AS = cast<llvm::PointerType>(Ptr->getType())->getAddressSpace();
+  llvm::Type *CharPtrTy = CGF.Builder.getInt8Ty()->getPointerTo(AS);
+
+  // If we don't need an array cookie, bail out early.
+  if (!NeedsArrayCookie(expr, ElementType)) {
+    AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy);
+    NumElements = 0;
+    CookieSize = CharUnits::Zero();
+    return;
+  }
+
+  QualType SizeTy = getContext().getSizeType();
+  CharUnits SizeSize = getContext().getTypeSizeInChars(SizeTy);
+  llvm::Type *SizeLTy = CGF.ConvertType(SizeTy);
+  
+  // The cookie size is always 2 * sizeof(size_t).
+  CookieSize = 2 * SizeSize;
+
+  // The allocated pointer is the input ptr, minus that amount.
+  AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy);
+  AllocPtr = CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr,
+                                               -CookieSize.getQuantity());
+
+  // The number of elements is at offset sizeof(size_t) relative to that.
+  llvm::Value *NumElementsPtr
+    = CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr,
+                                             SizeSize.getQuantity());
+  NumElementsPtr = 
+    CGF.Builder.CreateBitCast(NumElementsPtr, SizeLTy->getPointerTo(AS));
+  NumElements = CGF.Builder.CreateLoad(NumElementsPtr);
+}
+
+/*********************** Static local initialization **************************/
+
+static llvm::Constant *getGuardAcquireFn(CodeGenModule &CGM,
+                                         llvm::PointerType *GuardPtrTy) {
+  // int __cxa_guard_acquire(__guard *guard_object);
+  llvm::FunctionType *FTy =
+    llvm::FunctionType::get(CGM.getTypes().ConvertType(CGM.getContext().IntTy),
+                            GuardPtrTy, /*isVarArg=*/false);
+  
+  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire",
+                                   llvm::Attribute::NoUnwind);
+}
+
+static llvm::Constant *getGuardReleaseFn(CodeGenModule &CGM,
+                                         llvm::PointerType *GuardPtrTy) {
+  // void __cxa_guard_release(__guard *guard_object);
+  llvm::FunctionType *FTy =
+    llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
+  
+  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release",
+                                   llvm::Attribute::NoUnwind);
+}
+
+static llvm::Constant *getGuardAbortFn(CodeGenModule &CGM,
+                                       llvm::PointerType *GuardPtrTy) {
+  // void __cxa_guard_abort(__guard *guard_object);
+  llvm::FunctionType *FTy =
+    llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
+  
+  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort",
+                                   llvm::Attribute::NoUnwind);
+}
+
+namespace {
+  struct CallGuardAbort : EHScopeStack::Cleanup {
+    llvm::GlobalVariable *Guard;
+    CallGuardAbort(llvm::GlobalVariable *Guard) : Guard(Guard) {}
+
+    void Emit(CodeGenFunction &CGF, Flags flags) {
+      CGF.Builder.CreateCall(getGuardAbortFn(CGF.CGM, Guard->getType()), Guard)
+        ->setDoesNotThrow();
+    }
+  };
+}
+
+/// The ARM code here follows the Itanium code closely enough that we
+/// just special-case it at particular places.
+void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
+                                    const VarDecl &D,
+                                    llvm::GlobalVariable *var,
+                                    bool shouldPerformInit) {
+  CGBuilderTy &Builder = CGF.Builder;
+
+  // We only need to use thread-safe statics for local variables;
+  // global initialization is always single-threaded.
+  bool threadsafe =
+    (getContext().getLangOpts().ThreadsafeStatics && D.isLocalVarDecl());
+
+  // If we have a global variable with internal linkage and thread-safe statics
+  // are disabled, we can just let the guard variable be of type i8.
+  bool useInt8GuardVariable = !threadsafe && var->hasInternalLinkage();
+
+  llvm::IntegerType *guardTy;
+  if (useInt8GuardVariable) {
+    guardTy = CGF.Int8Ty;
+  } else {
+    // Guard variables are 64 bits in the generic ABI and 32 bits on ARM.
+    guardTy = (IsARM ? CGF.Int32Ty : CGF.Int64Ty);
+  }
+  llvm::PointerType *guardPtrTy = guardTy->getPointerTo();
+
+  // Create the guard variable if we don't already have it (as we
+  // might if we're double-emitting this function body).
+  llvm::GlobalVariable *guard = CGM.getStaticLocalDeclGuardAddress(&D);
+  if (!guard) {
+    // Mangle the name for the guard.
+    SmallString<256> guardName;
+    {
+      llvm::raw_svector_ostream out(guardName);
+      getMangleContext().mangleItaniumGuardVariable(&D, out);
+      out.flush();
+    }
+
+    // Create the guard variable with a zero-initializer.
+    // Just absorb linkage and visibility from the guarded variable.
+    guard = new llvm::GlobalVariable(CGM.getModule(), guardTy,
+                                     false, var->getLinkage(),
+                                     llvm::ConstantInt::get(guardTy, 0),
+                                     guardName.str());
+    guard->setVisibility(var->getVisibility());
+
+    CGM.setStaticLocalDeclGuardAddress(&D, guard);
+  }
+
+  // Test whether the variable has completed initialization.
+  llvm::Value *isInitialized;
+
+  // ARM C++ ABI 3.2.3.1:
+  //   To support the potential use of initialization guard variables
+  //   as semaphores that are the target of ARM SWP and LDREX/STREX
+  //   synchronizing instructions we define a static initialization
+  //   guard variable to be a 4-byte aligned, 4- byte word with the
+  //   following inline access protocol.
+  //     #define INITIALIZED 1
+  //     if ((obj_guard & INITIALIZED) != INITIALIZED) {
+  //       if (__cxa_guard_acquire(&obj_guard))
+  //         ...
+  //     }
+  if (IsARM && !useInt8GuardVariable) {
+    llvm::Value *V = Builder.CreateLoad(guard);
+    V = Builder.CreateAnd(V, Builder.getInt32(1));
+    isInitialized = Builder.CreateIsNull(V, "guard.uninitialized");
+
+  // Itanium C++ ABI 3.3.2:
+  //   The following is pseudo-code showing how these functions can be used:
+  //     if (obj_guard.first_byte == 0) {
+  //       if ( __cxa_guard_acquire (&obj_guard) ) {
+  //         try {
+  //           ... initialize the object ...;
+  //         } catch (...) {
+  //            __cxa_guard_abort (&obj_guard);
+  //            throw;
+  //         }
+  //         ... queue object destructor with __cxa_atexit() ...;
+  //         __cxa_guard_release (&obj_guard);
+  //       }
+  //     }
+  } else {
+    // Load the first byte of the guard variable.
+    llvm::LoadInst *LI = 
+      Builder.CreateLoad(Builder.CreateBitCast(guard, CGM.Int8PtrTy));
+    LI->setAlignment(1);
+
+    // Itanium ABI:
+    //   An implementation supporting thread-safety on multiprocessor
+    //   systems must also guarantee that references to the initialized
+    //   object do not occur before the load of the initialization flag.
+    //
+    // In LLVM, we do this by marking the load Acquire.
+    if (threadsafe)
+      LI->setAtomic(llvm::Acquire);
+
+    isInitialized = Builder.CreateIsNull(LI, "guard.uninitialized");
+  }
+
+  llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check");
+  llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
+
+  // Check if the first byte of the guard variable is zero.
+  Builder.CreateCondBr(isInitialized, InitCheckBlock, EndBlock);
+
+  CGF.EmitBlock(InitCheckBlock);
+
+  // Variables used when coping with thread-safe statics and exceptions.
+  if (threadsafe) {    
+    // Call __cxa_guard_acquire.
+    llvm::Value *V
+      = Builder.CreateCall(getGuardAcquireFn(CGM, guardPtrTy), guard);
+               
+    llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init");
+  
+    Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
+                         InitBlock, EndBlock);
+  
+    // Call __cxa_guard_abort along the exceptional edge.
+    CGF.EHStack.pushCleanup<CallGuardAbort>(EHCleanup, guard);
+    
+    CGF.EmitBlock(InitBlock);
+  }
+
+  // Emit the initializer and add a global destructor if appropriate.
+  CGF.EmitCXXGlobalVarDeclInit(D, var, shouldPerformInit);
+
+  if (threadsafe) {
+    // Pop the guard-abort cleanup if we pushed one.
+    CGF.PopCleanupBlock();
+
+    // Call __cxa_guard_release.  This cannot throw.
+    Builder.CreateCall(getGuardReleaseFn(CGM, guardPtrTy), guard);
+  } else {
+    Builder.CreateStore(llvm::ConstantInt::get(guardTy, 1), guard);
+  }
+
+  CGF.EmitBlock(EndBlock);
+}