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      1 //===--- AlignOf.h - Portable calculation of type alignment -----*- C++ -*-===//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 //
      9 // This file defines the AlignedCharArrayUnion class.
     10 //
     11 //===----------------------------------------------------------------------===//
     12 
     13 #ifndef LLVM_SUPPORT_ALIGNOF_H
     14 #define LLVM_SUPPORT_ALIGNOF_H
     15 
     16 #include <type_traits>
     17 
     18 namespace llvm {
     19 
     20 /// A suitably aligned and sized character array member which can hold elements
     21 /// of any type.
     22 ///
     23 /// This template is equivalent to std::aligned_union_t<1, ...>, but we cannot
     24 /// use it due to a bug in the MSVC x86 compiler:
     25 /// https://github.com/microsoft/STL/issues/1533
     26 /// Using `alignas` here works around the bug.
     27 template <typename T, typename... Ts> struct AlignedCharArrayUnion {
     28   using AlignedUnion = std::aligned_union_t<1, T, Ts...>;
     29   alignas(alignof(AlignedUnion)) char buffer[sizeof(AlignedUnion)];
     30 };
     31 
     32 } // end namespace llvm
     33 
     34 #endif // LLVM_SUPPORT_ALIGNOF_H
     35