2 files changed, 31 insertions, 41 deletions

diff --git a/llvm/include/llvm/Support/AlignOf.h b/llvm/include/llvm/Support/AlignOf.h
index 2d8297ee87d..abd19afa22f 100644
--- a/llvm/include/llvm/Support/AlignOf.h
+++ b/llvm/include/llvm/Support/AlignOf.h
@@ -102,37 +102,45 @@ LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(128)
 
 #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 support {
 namespace detail {
-template <typename T1> constexpr size_t aligner() { return alignof(T1); }
-
-template <typename T1, typename T2, typename... Ts> constexpr size_t aligner() {
-  return (alignof(T1) > aligner<T2, Ts...>()) ? alignof(T1)
-                                              : aligner<T2, Ts...>();
-}
-
-template <typename T1> constexpr size_t sizer() { return sizeof(T1); }
+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;
+
+  AlignerImpl() = delete;
+};
 
-template <typename T1, typename T2, typename... Ts> constexpr size_t sizer() {
-  return (sizeof(T1) > sizer<T2, Ts...>()) ? sizeof(T1) : sizer<T2, Ts...>();
-}
+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)];
+};
 } // end namespace detail
-} // end namespace support
 
 /// \brief This union template exposes a suitably aligned and sized character
-/// array member which can hold elements of any of a number of types.
+/// array member which can hold elements of any of up to ten 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.
-template <typename... Ts>
-struct AlignedCharArrayUnion
-    : llvm::AlignedCharArray<support::detail::aligner<Ts...>(),
-                             support::detail::sizer<Ts...>()> {};
+/// 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>)> {
+};
 } // end namespace llvm
 
 #endif // LLVM_SUPPORT_ALIGNOF_H
diff --git a/llvm/unittests/Support/AlignOfTest.cpp b/llvm/unittests/Support/AlignOfTest.cpp
index dfcdc1484b3..388ca11b776 100644
--- a/llvm/unittests/Support/AlignOfTest.cpp
+++ b/llvm/unittests/Support/AlignOfTest.cpp
@@ -91,24 +91,6 @@ V8::~V8() {}
 
 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>));