[PATCH] D11272: Add a TrailingObjects template class.

Justin Bogner mail at justinbogner.com
Mon Aug 3 15:59:53 PDT 2015


James Y Knight <jyknight at google.com> writes:
> jyknight updated this revision to Diff 31242.
> jyknight added a comment.
>
> Switched to doxygen comment style, extracted the is_final as an
> LLVM_IS_FINAL macro.

A couple more comments below, then this LGTM.

>
> http://reviews.llvm.org/D11272
>
> Files:
>   include/llvm/Support/TrailingObjects.h
>   include/llvm/Support/type_traits.h
>   lib/IR/AttributeImpl.h
>   lib/IR/Attributes.cpp
>   unittests/Support/CMakeLists.txt
>   unittests/Support/TrailingObjectsTest.cpp
>
> Index: unittests/Support/TrailingObjectsTest.cpp
> ===================================================================
> --- /dev/null
> +++ unittests/Support/TrailingObjectsTest.cpp
> @@ -0,0 +1,147 @@
> +//=== - llvm/unittest/Support/TrailingObjectsTest.cpp ---------------------===//
> +//
> +//                     The LLVM Compiler Infrastructure
> +//
> +// This file is distributed under the University of Illinois Open Source
> +// License. See LICENSE.TXT for details.
> +//
> +//===----------------------------------------------------------------------===//
> +
> +#include "llvm/Support/TrailingObjects.h"
> +#include "gtest/gtest.h"
> +
> +using namespace llvm;
> +
> +namespace {
> +// This class, beyond being used by the test case, a nice
> +// demonstration of the intended usage of TrailingObjects, with a
> +// single trailing array.
> +class Class1 final : TrailingObjects<Class1, short> {
> +  friend class TrailingObjects;
> +
> +  unsigned NumShorts;
> +
> +protected:
> +  size_t numTrailingObjects(OverloadToken<short>) const { return NumShorts; }
> +
> +  Class1(int *ShortArray, unsigned NumShorts) : NumShorts(NumShorts) {
> +    std::uninitialized_copy(ShortArray, ShortArray + NumShorts,
> +                            getTrailingObjects<short>());
> +  }
> +
> +public:
> +  static Class1 *create(int *ShortArray, unsigned NumShorts) {
> +    void *Mem = ::operator new(totalSizeToAlloc<short>(NumShorts));
> +    return new (Mem) Class1(ShortArray, NumShorts);
> +  }
> +
> +  short get(unsigned Num) const { return getTrailingObjects<short>()[Num]; }
> +
> +  unsigned numShorts() const { return NumShorts; }
> +
> +  // Pull some protected members in as public, for testability.
> +  using TrailingObjects::totalSizeToAlloc;
> +  using TrailingObjects::additionalSizeToAlloc;
> +  using TrailingObjects::getTrailingObjects;
> +};
> +
> +// Here, there are two singular optional object types appended.
> +// Note that it fails to compile without the alignment spec.
> +class LLVM_ALIGNAS(8) Class2 final : TrailingObjects<Class2, double, short> {
> +  friend class TrailingObjects;
> +
> +  bool HasShort, HasDouble;
> +
> +protected:
> +  size_t numTrailingObjects(OverloadToken<short>) const {
> +    return HasShort ? 1 : 0;
> +  }
> +  size_t numTrailingObjects(OverloadToken<double>) const {
> +    return HasDouble ? 1 : 0;
> +  }
> +
> +  Class2(bool HasShort, bool HasDouble)
> +      : HasShort(HasShort), HasDouble(HasDouble) {}
> +
> +public:
> +  static Class2 *create(short S = 0, double D = 0.0) {
> +    bool HasShort = S != 0;
> +    bool HasDouble = D != 0.0;
> +
> +    void *Mem =
> +        ::operator new(totalSizeToAlloc<double, short>(HasDouble, HasShort));
> +    Class2 *C = new (Mem) Class2(HasShort, HasDouble);
> +    if (HasShort)
> +      *C->getTrailingObjects<short>() = S;
> +    if (HasDouble)
> +      *C->getTrailingObjects<double>() = D;
> +    return C;
> +  }
> +
> +  short getShort() const {
> +    if (!HasShort)
> +      return 0;
> +    return *getTrailingObjects<short>();
> +  }
> +
> +  double getDouble() const {
> +    if (!HasDouble)
> +      return 0.0;
> +    return *getTrailingObjects<double>();
> +  }
> +
> +  // Pull some protected members in as public, for testability.
> +  using TrailingObjects::totalSizeToAlloc;
> +  using TrailingObjects::additionalSizeToAlloc;
> +  using TrailingObjects::getTrailingObjects;
> +};
> +
> +TEST(TrailingObjects, OneArg) {
> +  int arr[] = {1, 2, 3};
> +  Class1 *C = Class1::create(arr, 3);
> +  EXPECT_EQ(sizeof(Class1), sizeof(unsigned));
> +  EXPECT_EQ(Class1::additionalSizeToAlloc<short>(1), sizeof(short));
> +  EXPECT_EQ(Class1::additionalSizeToAlloc<short>(3), sizeof(short) * 3);
> +
> +  EXPECT_EQ(Class1::totalSizeToAlloc<short>(1), sizeof(Class1) + sizeof(short));
> +  EXPECT_EQ(Class1::totalSizeToAlloc<short>(3),
> +            sizeof(Class1) + sizeof(short) * 3);
> +
> +  EXPECT_EQ(C->getTrailingObjects<short>(), reinterpret_cast<short *>(C + 1));
> +  EXPECT_EQ(C->get(0), 1);
> +  EXPECT_EQ(C->get(2), 3);
> +  delete C;
> +}
> +
> +TEST(TrailingObjects, TwoArg) {
> +  Class2 *C1 = Class2::create(4);
> +  Class2 *C2 = Class2::create(0, 4.2);
> +
> +  EXPECT_EQ(sizeof(Class2), 8u); // due to alignment
> +
> +  EXPECT_EQ((Class2::additionalSizeToAlloc<double, short>(1, 0)),
> +            sizeof(double));
> +  EXPECT_EQ((Class2::additionalSizeToAlloc<double, short>(0, 1)),
> +            sizeof(short));
> +  EXPECT_EQ((Class2::additionalSizeToAlloc<double, short>(3, 1)),
> +            sizeof(double) * 3 + sizeof(short));
> +
> +  EXPECT_EQ((Class2::totalSizeToAlloc<double, short>(1, 1)),
> +            sizeof(Class2) + sizeof(double) + sizeof(short));
> +
> +  EXPECT_EQ(C1->getDouble(), 0);
> +  EXPECT_EQ(C1->getShort(), 4);
> +  EXPECT_EQ(C1->getTrailingObjects<double>(),
> +            reinterpret_cast<double *>(C1 + 1));
> +  EXPECT_EQ(C1->getTrailingObjects<short>(), reinterpret_cast<short *>(C1 + 1));
> +
> +  EXPECT_EQ(C2->getDouble(), 4.2);
> +  EXPECT_EQ(C2->getShort(), 0);
> +  EXPECT_EQ(C2->getTrailingObjects<double>(),
> +            reinterpret_cast<double *>(C2 + 1));
> +  EXPECT_EQ(C2->getTrailingObjects<short>(),
> +            reinterpret_cast<short *>(reinterpret_cast<double *>(C2 + 1) + 1));
> +  delete C1;
> +  delete C2;
> +}
> +}
> Index: unittests/Support/CMakeLists.txt
> ===================================================================
> --- unittests/Support/CMakeLists.txt
> +++ unittests/Support/CMakeLists.txt
> @@ -41,6 +41,7 @@
>    TargetRegistry.cpp
>    ThreadLocalTest.cpp
>    TimeValueTest.cpp
> +  TrailingObjectsTest.cpp
>    UnicodeTest.cpp
>    YAMLIOTest.cpp
>    YAMLParserTest.cpp
> Index: lib/IR/Attributes.cpp
> ===================================================================
> --- lib/IR/Attributes.cpp
> +++ lib/IR/Attributes.cpp
> @@ -484,8 +484,7 @@
>    // new one and insert it.
>    if (!PA) {
>      // Coallocate entries after the AttributeSetNode itself.
> -    void *Mem = ::operator new(sizeof(AttributeSetNode) +
> -                               sizeof(Attribute) * SortedAttrs.size());
> +    void *Mem = ::operator new(totalSizeToAlloc<Attribute>(SortedAttrs.size()));
>      PA = new (Mem) AttributeSetNode(SortedAttrs);
>      pImpl->AttrsSetNodes.InsertNode(PA, InsertPoint);
>    }
> @@ -617,9 +616,8 @@
>    // create a new one and insert it.
>    if (!PA) {
>      // Coallocate entries after the AttributeSetImpl itself.
> -    void *Mem = ::operator new(sizeof(AttributeSetImpl) +
> -                               sizeof(std::pair<unsigned, AttributeSetNode *>) *
> -                                   Attrs.size());
> +    void *Mem = ::operator new(
> +        AttributeSetImpl::totalSizeToAlloc<IndexAttrPair>(Attrs.size()));
>      PA = new (Mem) AttributeSetImpl(C, Attrs);
>      pImpl->AttrsLists.InsertNode(PA, InsertPoint);
>    }
> @@ -736,9 +734,8 @@
>      if (!AS) continue;
>      SmallVector<std::pair<unsigned, AttributeSetNode *>, 8>::iterator
>        ANVI = AttrNodeVec.begin(), ANVE;
> -    for (const AttributeSetImpl::IndexAttrPair
> -             *AI = AS->getNode(0),
> -             *AE = AS->getNode(AS->getNumAttributes());
> +    for (const IndexAttrPair *AI = AS->getNode(0),
> +                             *AE = AS->getNode(AS->getNumAttributes());
>           AI != AE; ++AI) {
>        ANVE = AttrNodeVec.end();
>        while (ANVI != ANVE && ANVI->first <= AI->first)
> Index: lib/IR/AttributeImpl.h
> ===================================================================
> --- lib/IR/AttributeImpl.h
> +++ lib/IR/AttributeImpl.h
> @@ -18,6 +18,7 @@
>  
>  #include "llvm/ADT/FoldingSet.h"
>  #include "llvm/IR/Attributes.h"
> +#include "llvm/Support/TrailingObjects.h"
>  #include <string>
>  
>  namespace llvm {
> @@ -141,13 +142,14 @@
>  /// \class
>  /// \brief This class represents a group of attributes that apply to one
>  /// element: function, return type, or parameter.
> -class AttributeSetNode : public FoldingSetNode {
> +class AttributeSetNode final
> +    : public FoldingSetNode,
> +      public TrailingObjects<AttributeSetNode, Attribute> {

This should probably be private inheritance, shouldn't it? We don't need
or want is-a here.

>    unsigned NumAttrs; ///< Number of attributes in this node.
>  
>    AttributeSetNode(ArrayRef<Attribute> Attrs) : NumAttrs(Attrs.size()) {
>      // There's memory after the node where we can store the entries in.
> -    std::copy(Attrs.begin(), Attrs.end(),
> -              reinterpret_cast<Attribute *>(this + 1));
> +    std::copy(Attrs.begin(), Attrs.end(), getTrailingObjects<Attribute>());
>    }
>  
>    // AttributesSetNode is uniqued, these should not be publicly available.
> @@ -170,7 +172,7 @@
>    std::string getAsString(bool InAttrGrp) const;
>  
>    typedef const Attribute *iterator;
> -  iterator begin() const { return reinterpret_cast<iterator>(this + 1); }
> +  iterator begin() const { return getTrailingObjects<Attribute>(); }
>    iterator end() const { return begin() + NumAttrs; }
>  
>    void Profile(FoldingSetNodeID &ID) const {
> @@ -181,27 +183,28 @@
>        AttrList[I].Profile(ID);
>    }
>  };
> -static_assert(
> -    AlignOf<AttributeSetNode>::Alignment >= AlignOf<Attribute>::Alignment,
> -    "Alignment is insufficient for objects appended to AttributeSetNode");
>  
>  //===----------------------------------------------------------------------===//
>  /// \class
>  /// \brief This class represents a set of attributes that apply to the function,
>  /// return type, and parameters.
> -class AttributeSetImpl : public FoldingSetNode {
> -  friend class AttributeSet;
> +typedef std::pair<unsigned, AttributeSetNode *> IndexAttrPair;
>  
> -public:
> -  typedef std::pair<unsigned, AttributeSetNode*> IndexAttrPair;
> +class AttributeSetImpl final
> +    : public FoldingSetNode,
> +      public TrailingObjects<AttributeSetImpl, IndexAttrPair> {
> +  friend class AttributeSet;
>  
>  private:
>    LLVMContext &Context;
>    unsigned NumAttrs; ///< Number of entries in this set.
>  
> +  // Helper fn for TrailingObjects class.
> +  size_t numTrailingObjects(OverloadToken<IndexAttrPair>) { return NumAttrs; }
> +
>    /// \brief Return a pointer to the IndexAttrPair for the specified slot.
>    const IndexAttrPair *getNode(unsigned Slot) const {
> -    return reinterpret_cast<const IndexAttrPair *>(this + 1) + Slot;
> +    return getTrailingObjects<IndexAttrPair>() + Slot;
>    }
>  
>    // AttributesSet is uniqued, these should not be publicly available.
> @@ -222,8 +225,7 @@
>      }
>  #endif
>      // There's memory after the node where we can store the entries in.
> -    std::copy(Attrs.begin(), Attrs.end(),
> -              reinterpret_cast<IndexAttrPair *>(this + 1));
> +    std::copy(Attrs.begin(), Attrs.end(), getTrailingObjects<IndexAttrPair>());
>    }
>  
>    /// \brief Get the context that created this AttributeSetImpl.
> @@ -273,10 +275,6 @@
>  
>    void dump() const;
>  };
> -static_assert(
> -    AlignOf<AttributeSetImpl>::Alignment >=
> -        AlignOf<AttributeSetImpl::IndexAttrPair>::Alignment,
> -    "Alignment is insufficient for objects appended to AttributeSetImpl");
>  
>  } // end llvm namespace
>  
> Index: include/llvm/Support/type_traits.h
> ===================================================================
> --- include/llvm/Support/type_traits.h
> +++ include/llvm/Support/type_traits.h
> @@ -93,6 +93,15 @@
>  
>  }
>  
> +// If the compiler supports detecting whether a class is final, define
> +// an LLVM_IS_FINAL macro. If it cannot be defined properly, this
> +// macro will be left undefined.
> +#if __cplusplus >= 201402L
> +#define LLVM_IS_FINAL(Ty) std::is_final<Ty>()
> +#elif __has_feature(is_final) || LLVM_GNUC_PREREQ(4, 7, 0)
> +#define LLVM_IS_FINAL(Ty) __is_final(Ty)
> +#endif
> +
>  #ifdef LLVM_DEFINED_HAS_FEATURE
>  #undef __has_feature
>  #endif
> Index: include/llvm/Support/TrailingObjects.h
> ===================================================================
> --- /dev/null
> +++ include/llvm/Support/TrailingObjects.h
> @@ -0,0 +1,234 @@
> +//===--- TrailingObjects.h - Variable-length classes ------------*- C++ -*-===//
> +//
> +//                     The LLVM Compiler Infrastructure
> +//
> +// This file is distributed under the University of Illinois Open Source
> +// License. See LICENSE.TXT for details.
> +//
> +//===----------------------------------------------------------------------===//
> +///
> +/// \file
> +/// This header defines support for implementing classes that have
> +/// some trailing object (or arrays of objects) appended to them. The
> +/// main purpose is to make it obvious where this idiom is being used,
> +/// and to make the usage more idiomatic and more difficult to get
> +/// wrong.
> +///
> +/// The TrailingObject template abstracts away the reinterpret_cast,
> +/// pointer arithmetic, and size calculations used for the allocation
> +/// and access of appended arrays of objects, as well as asserts that
> +/// the alignment of the classes involved are appropriate for the
> +/// usage. Additionally, it ensures that the base type is final --
> +/// deriving from a class that expects data appended immediately after
> +/// it is typically not safe.
> +///
> +/// Users are expected to derive from this template, and provide
> +/// numTrailingObjects implementations for each trailing type,
> +/// e.g. like this sample:
> +///
> +/// \code
> +/// class VarLengthObj : TrailingObjects<VarLengthObj, int, double> {
> +///   friend class TrailingObjects;
> +///
> +///   unsigned NumInts, NumDoubles;
> +///   size_t numTrailingObjects(OverloadToken<int>) const { return NumInts; }
> +///   size_t numTrailingObjects(OverloadToken<double>) const {
> +///     return NumDoubles;
> +///   }
> +///  };
> +/// \endcode
> +///
> +/// You can access the appended arrays via 'getTrailingObjects', and
> +/// determine the size needed for allocation via
> +/// 'additionalSizeToAlloc' and 'totalSizeToAlloc'.
> +///
> +/// All the methods implemented by this class are protected -- they
> +/// are intended for use by the implementation of the class, not as
> +/// part of its interface.

This won't be necessary if subclasses use private inheritance.

> +///
> +//===----------------------------------------------------------------------===//
> +
> +#ifndef LLVM_SUPPORT_TRAILINGOBJECTS_H
> +#define LLVM_SUPPORT_TRAILINGOBJECTS_H
> +
> +#include <new>
> +#include <type_traits>
> +#include "llvm/Support/AlignOf.h"
> +#include "llvm/Support/type_traits.h"
> +
> +namespace llvm {
> +
> +/// The base class for TrailingObjects* classes.
> +class TrailingObjectsBase {
> +protected:
> +  /// OverloadToken's purpose is to allow specifying function overloads
> +  /// for different types, without actually taking the types as
> +  /// parameters. (Necessary because member function templates cannot
> +  /// be specialized, so overloads must be used instead of
> +  /// specialization.)
> +  template <typename T> struct OverloadToken {};
> +};
> +
> +// Internally used to indicate that the user didn't supply this value,
> +// so the explicit-specialization for fewer args will be used.
> +class NoTrailingTypeArg {};
> +
> +// TODO: Consider using a single variadic implementation instead of
> +// multiple copies of the TrailingObjects template? [but, variadic
> +// template recursive implementations are annoying...]
> +
> +/// This is the two-type version of the TrailingObjects template; see
> +/// file docstring for details.
> +template <typename BaseTy, typename TrailingTy1,
> +          typename TrailingTy2 = NoTrailingTypeArg>
> +class TrailingObjects : public TrailingObjectsBase {
> +private:
> +  // Contains static_assert statements for the alignment of the
> +  // types. Must not be at class-level, because BaseTy isn't complete
> +  // at class instantiation time, but will be by the time this
> +  // function is instantiated.
> +  static void verifyTrailingObjectsAssertions() {
> +    static_assert(llvm::AlignOf<BaseTy>::Alignment >=
> +                      llvm::AlignOf<TrailingTy1>::Alignment,
> +                  "TrailingTy1 requires more alignment than BaseTy provides");
> +    static_assert(
> +        llvm::AlignOf<TrailingTy1>::Alignment >=
> +            llvm::AlignOf<TrailingTy2>::Alignment,
> +        "TrailingTy2 requires more alignment than TrailingTy1 provides");
> +
> +#ifdef LLVM_IS_FINAL
> +    static_assert(LLVM_IS_FINAL(BaseTy), "BaseTy must be final.");
> +#endif
> +  }
> +
> +  // The next four functions are internal helpers for getTrailingObjects.
> +  static const TrailingTy1 *getTrailingObjectsImpl(const BaseTy *Obj,
> +                                                   OverloadToken<TrailingTy1>) {
> +    return reinterpret_cast<const TrailingTy1 *>(Obj + 1);
> +  }
> +
> +  static TrailingTy1 *getTrailingObjectsImpl(BaseTy *Obj,
> +                                             OverloadToken<TrailingTy1>) {
> +    return reinterpret_cast<TrailingTy1 *>(Obj + 1);
> +  }
> +
> +  static const TrailingTy2 *getTrailingObjectsImpl(const BaseTy *Obj,
> +                                                   OverloadToken<TrailingTy2>) {
> +    return reinterpret_cast<const TrailingTy2 *>(
> +        getTrailingObjectsImpl(Obj, OverloadToken<TrailingTy1>()) +
> +        Obj->numTrailingObjects(OverloadToken<TrailingTy1>()));
> +  }
> +
> +  static TrailingTy2 *getTrailingObjectsImpl(BaseTy *Obj,
> +                                             OverloadToken<TrailingTy2>) {
> +    return reinterpret_cast<TrailingTy2 *>(
> +        getTrailingObjectsImpl(Obj, OverloadToken<TrailingTy1>()) +
> +        Obj->numTrailingObjects(OverloadToken<TrailingTy1>()));
> +  }
> +
> +protected:
> +  /// Returns a pointer to the trailing object array of the given type
> +  /// (which must be one of those specified in the class template). The
> +  /// array may have zero or more elements in it.
> +  template <typename T> const T *getTrailingObjects() const {
> +    verifyTrailingObjectsAssertions();
> +    // Forwards to an impl function with overloads, since member
> +    // function templates can't be specialized.
> +    return getTrailingObjectsImpl(static_cast<const BaseTy *>(this),
> +                                  OverloadToken<T>());
> +  }
> +
> +  /// Returns a pointer to the trailing object array of the given type
> +  /// (which must be one of those specified in the class template). The
> +  /// array may have zero or more elements in it.
> +  template <typename T> T *getTrailingObjects() {
> +    verifyTrailingObjectsAssertions();
> +    // Forwards to an impl function with overloads, since member
> +    // function templates can't be specialized.
> +    return getTrailingObjectsImpl(static_cast<BaseTy *>(this),
> +                                  OverloadToken<T>());
> +  }
> +
> +  /// Returns the size of the trailing data, if an object were
> +  /// allocated with the given counts (The counts are in the same order
> +  /// as the template arguments). This does not include the size of the
> +  /// base object.  The template arguments must be the same as those
> +  /// used in the class; they are supplied here redundantly only so
> +  /// that it's clear what the counts are counting in callers.
> +  template <typename Ty1, typename Ty2,
> +            typename std::enable_if<std::is_same<Ty1, TrailingTy1>::value &&
> +                                        std::is_same<Ty2, TrailingTy2>::value,
> +                                    int>::type = 0>
> +  static constexpr size_t additionalSizeToAlloc(size_t Count1, size_t Count2) {
> +    return sizeof(TrailingTy1) * Count1 + sizeof(TrailingTy2) * Count2;
> +  }
> +
> +  /// Returns the total size of an object if it were allocated with the
> +  /// given trailing object counts. This is the same as
> +  /// additionalSizeToAlloc, except it *does* include the size of the base
> +  /// object.
> +  template <typename Ty1, typename Ty2>
> +  static constexpr size_t totalSizeToAlloc(size_t Count1, size_t Count2) {
> +    return sizeof(BaseTy) + additionalSizeToAlloc<Ty1, Ty2>(Count1, Count2);
> +  }
> +};
> +
> +/// This is the one-type version of the TrailingObjects template. See
> +/// the two-type version for more documentation.
> +template <typename BaseTy, typename TrailingTy1>
> +class TrailingObjects<BaseTy, TrailingTy1, NoTrailingTypeArg>
> +    : public TrailingObjectsBase {
> +private:
> +  static void verifyTrailingObjectsAssertions() {
> +    static_assert(llvm::AlignOf<BaseTy>::Alignment >=
> +                      llvm::AlignOf<TrailingTy1>::Alignment,
> +                  "TrailingTy1 requires more alignment than BaseTy provides");
> +
> +#ifdef LLVM_IS_FINAL
> +    static_assert(LLVM_IS_FINAL(BaseTy), "BaseTy must be final.");
> +#endif
> +  }
> +
> +  static const TrailingTy1 *getTrailingObjectsImpl(const BaseTy *Obj,
> +                                                   OverloadToken<TrailingTy1>) {
> +    return reinterpret_cast<const TrailingTy1 *>(Obj + 1);
> +  }
> +
> +  static TrailingTy1 *getTrailingObjectsImpl(BaseTy *Obj,
> +                                             OverloadToken<TrailingTy1>) {
> +    return reinterpret_cast<TrailingTy1 *>(Obj + 1);
> +  }
> +
> +protected:
> +  template <typename T> const T *getTrailingObjects() const {
> +    verifyTrailingObjectsAssertions();
> +    return getTrailingObjectsImpl(static_cast<const BaseTy *>(this),
> +                                  OverloadToken<T>());
> +  }
> +
> +  template <typename T> T *getTrailingObjects() {
> +    verifyTrailingObjectsAssertions();
> +    return getTrailingObjectsImpl(static_cast<BaseTy *>(this),
> +                                  OverloadToken<T>());
> +  }
> +
> +  template <typename Ty1,
> +            typename std::enable_if<std::is_same<Ty1, TrailingTy1>::value,
> +                                    int>::type = 0>
> +  static constexpr size_t additionalSizeToAlloc(size_t Count1) {
> +    return sizeof(TrailingTy1) * Count1;
> +  }
> +
> +  template <typename Ty1>
> +  static constexpr size_t totalSizeToAlloc(size_t Count1) {
> +    return sizeof(BaseTy) + additionalSizeToAlloc<Ty1>(Count1);
> +  }
> +};
> +
> +} // end namespace llvm
> +
> +#ifdef LLVM_DEFINED_HAS_FEATURE
> +#undef __has_feature
> +#endif

Remove this, it's left over from a previous version.

> +
> +#endif



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