[PATCH] D28429: Remove the restriction of ten types on AligedCharArrayUnion

[David Blaikie via llvm-commits]

Thanks - please commit whenever you're ready to do so

On Mon, Jan 9, 2017 at 1:39 PM Sean Callanan via Phabricator <
reviews at reviews.llvm.org> wrote:

> spyffe set the repository for this revision to rL LLVM.
> spyffe updated this revision to Diff 83679.
> spyffe added a comment.
>
> Added a comment at David's request, and moved the test into the
> Support/AlignOf unit tests.  Also removed the `memcpy` test.
>
>
> Repository:
>   rL LLVM
>
> https://reviews.llvm.org/D28429
>
> Files:
>   include/llvm/Support/AlignOf.h
>   unittests/Support/AlignOfTest.cpp
>
>
> Index: unittests/Support/AlignOfTest.cpp
> ===================================================================
> --- unittests/Support/AlignOfTest.cpp
> +++ unittests/Support/AlignOfTest.cpp
> @@ -91,6 +91,24 @@
>
>  template <typename M> struct T { M m; };
>
> +typedef uint8_t t1;
> +typedef uint16_t t2;
> +typedef uint32_t t3;
> +typedef uint64_t t4;
> +typedef int8_t t5;
> +typedef int16_t t6;
> +typedef int32_t t7;
> +typedef int64_t t8;
> +typedef struct { uint8_t bytes[16]; } t9;
> +typedef struct { uint16_t words[16]; } t10;
> +typedef struct { uint32_t words[16]; } t11;
> +typedef struct { uint64_t words[16]; } t12;
> +
> +typedef AlignedCharArrayUnion<t1, t2, t3, t4, t5, t6, t7, t8, t9, t10,
> t11, t12> U;
> +
> +static_assert(sizeof(U) == sizeof(uint64_t[16]), "Statically-computed
> size must be right");
> +static_assert(alignof(U) == alignof(uint64_t), "Statically-computed
> alignment must be right");
> +
>  TEST(AlignOfTest, BasicAlignedArray) {
>    EXPECT_LE(1u, alignof(AlignedCharArrayUnion<A1>));
>    EXPECT_LE(2u, alignof(AlignedCharArrayUnion<A2>));
> Index: include/llvm/Support/AlignOf.h
> ===================================================================
> --- include/llvm/Support/AlignOf.h
> +++ include/llvm/Support/AlignOf.h
> @@ -102,45 +102,38 @@
>
>  #endif // _MSC_VER
>
> +// This code implements the equivalent of std::aligned_union from C++11.
> +// That is supported by Visual Studio 2015 and GCC 5.1.
> +// Once these are the baselines for LLVM, we can use std::aligned_union
> instead.
> +
>  namespace detail {
> -template <typename T1,
> -          typename T2 = char, typename T3 = char, typename T4 = char,
> -          typename T5 = char, typename T6 = char, typename T7 = char,
> -          typename T8 = char, typename T9 = char, typename T10 = char>
> -class AlignerImpl {
> -  T1 t1; T2 t2; T3 t3; T4 t4; T5 t5; T6 t6; T7 t7; T8 t8; T9 t9; T10 t10;
> +template <typename... Ts> class AlignerImpl;
>
> +template <typename T1, typename... Ts>
> +class AlignerImpl<T1, Ts...> : AlignerImpl<Ts...> {
> +  T1 t;
>    AlignerImpl() = delete;
>  };
>
> -template <typename T1,
> -          typename T2 = char, typename T3 = char, typename T4 = char,
> -          typename T5 = char, typename T6 = char, typename T7 = char,
> -          typename T8 = char, typename T9 = char, typename T10 = char>
> -union SizerImpl {
> -  char arr1[sizeof(T1)], arr2[sizeof(T2)], arr3[sizeof(T3)],
> arr4[sizeof(T4)],
> -       arr5[sizeof(T5)], arr6[sizeof(T6)], arr7[sizeof(T7)],
> arr8[sizeof(T8)],
> -       arr9[sizeof(T9)], arr10[sizeof(T10)];
> -};
> +template <> class AlignerImpl<> { AlignerImpl() = delete; };
> +
> +template <typename T1> constexpr size_t sizer() { return sizeof(T1); }
> +
> +template <typename T1, typename T2, typename... Ts> constexpr size_t
> sizer() {
> +  return (sizeof(T1) > sizer<T2, Ts...>()) ? sizeof(T1) : sizer<T2,
> Ts...>();
> +}
>  } // end namespace detail
>
>  /// \brief This union template exposes a suitably aligned and sized
> character
> -/// array member which can hold elements of any of up to ten types.
> +/// array member which can hold elements of any of a number of types.
>  ///
>  /// These types may be arrays, structs, or any other types. The goal is to
>  /// expose a char array buffer member which can be used as suitable
> storage for
> -/// a placement new of any of these types. Support for more than ten
> types can
> -/// be added at the cost of more boilerplate.
> -template <typename T1,
> -          typename T2 = char, typename T3 = char, typename T4 = char,
> -          typename T5 = char, typename T6 = char, typename T7 = char,
> -          typename T8 = char, typename T9 = char, typename T10 = char>
> -struct AlignedCharArrayUnion : llvm::AlignedCharArray<
> -    alignof(llvm::detail::AlignerImpl<T1, T2, T3, T4, T5,
> -                                      T6, T7, T8, T9, T10>),
> -    sizeof(::llvm::detail::SizerImpl<T1, T2, T3, T4, T5,
> -                                     T6, T7, T8, T9, T10>)> {
> -};
> +/// a placement new of any of these types.
> +template <typename... Ts>
> +struct AlignedCharArrayUnion
> +    : llvm::AlignedCharArray<alignof(llvm::detail::AlignerImpl<Ts...>),
> +                             detail::sizer<Ts...>()> {};
>  } // end namespace llvm
>
>  #endif // LLVM_SUPPORT_ALIGNOF_H
>
>
>
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