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//===--- AlignOf.h - Portable calculation of type alignment -----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the AlignOf function that computes alignments for
// arbitrary types.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_ALIGNOF_H
#define LLVM_SUPPORT_ALIGNOF_H
#include "llvm/Support/Compiler.h"
#include <cstddef>
namespace llvm {template <typename T>struct AlignmentCalcImpl { char x; T t;private: AlignmentCalcImpl() {} // Never instantiate.
};
/// AlignOf - A templated class that contains an enum value representing
/// the alignment of the template argument. For example,
/// AlignOf<int>::Alignment represents the alignment of type "int". The
/// alignment calculated is the minimum alignment, and not necessarily
/// the "desired" alignment returned by GCC's __alignof__ (for example). Note
/// that because the alignment is an enum value, it can be used as a
/// compile-time constant (e.g., for template instantiation).
template <typename T>struct AlignOf { enum { Alignment = static_cast<unsigned int>(sizeof(AlignmentCalcImpl<T>) - sizeof(T)) };
enum { Alignment_GreaterEqual_2Bytes = Alignment >= 2 ? 1 : 0 }; enum { Alignment_GreaterEqual_4Bytes = Alignment >= 4 ? 1 : 0 }; enum { Alignment_GreaterEqual_8Bytes = Alignment >= 8 ? 1 : 0 }; enum { Alignment_GreaterEqual_16Bytes = Alignment >= 16 ? 1 : 0 };
enum { Alignment_LessEqual_2Bytes = Alignment <= 2 ? 1 : 0 }; enum { Alignment_LessEqual_4Bytes = Alignment <= 4 ? 1 : 0 }; enum { Alignment_LessEqual_8Bytes = Alignment <= 8 ? 1 : 0 }; enum { Alignment_LessEqual_16Bytes = Alignment <= 16 ? 1 : 0 };};
/// alignOf - A templated function that returns the minimum alignment of
/// of a type. This provides no extra functionality beyond the AlignOf
/// class besides some cosmetic cleanliness. Example usage:
/// alignOf<int>() returns the alignment of an int.
template <typename T>inline unsigned alignOf() { return AlignOf<T>::Alignment; }
/// \struct AlignedCharArray
/// \brief Helper for building an aligned character array type.
///
/// This template is used to explicitly build up a collection of aligned
/// character array types. We have to build these up using a macro and explicit
/// specialization to cope with old versions of MSVC and GCC where only an
/// integer literal can be used to specify an alignment constraint. Once built
/// up here, we can then begin to indirect between these using normal C++
/// template parameters.
// MSVC requires special handling here.
#ifndef _MSC_VER
#if __has_feature(cxx_alignas)
template<std::size_t Alignment, std::size_t Size>struct AlignedCharArray { alignas(Alignment) char buffer[Size];};
#elif defined(__GNUC__) || defined(__IBM_ATTRIBUTES)
/// \brief Create a type with an aligned char buffer.
template<std::size_t Alignment, std::size_t Size>struct AlignedCharArray;
#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
template<std::size_t Size> \ struct AlignedCharArray<x, Size> { \ __attribute__((aligned(x))) char buffer[Size]; \ };
LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(1)LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(2)LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(4)LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(8)LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(16)LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(32)LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(64)LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(128)
#undef LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT
#else
# error No supported align as directive.
#endif
#else // _MSC_VER
/// \brief Create a type with an aligned char buffer.
template<std::size_t Alignment, std::size_t Size>struct AlignedCharArray;
// We provide special variations of this template for the most common
// alignments because __declspec(align(...)) doesn't actually work when it is
// a member of a by-value function argument in MSVC, even if the alignment
// request is something reasonably like 8-byte or 16-byte. Note that we can't
// even include the declspec with the union that forces the alignment because
// MSVC warns on the existence of the declspec despite the union member forcing
// proper alignment.
template<std::size_t Size>struct AlignedCharArray<1, Size> { union { char aligned; char buffer[Size]; };};
template<std::size_t Size>struct AlignedCharArray<2, Size> { union { short aligned; char buffer[Size]; };};
template<std::size_t Size>struct AlignedCharArray<4, Size> { union { int aligned; char buffer[Size]; };};
template<std::size_t Size>struct AlignedCharArray<8, Size> { union { double aligned; char buffer[Size]; };};
// The rest of these are provided with a __declspec(align(...)) and we simply
// can't pass them by-value as function arguments on MSVC.
#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
template<std::size_t Size> \ struct AlignedCharArray<x, Size> { \ __declspec(align(x)) char buffer[Size]; \ };
LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(16)LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(32)LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(64)LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(128)
#undef LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT
#endif // _MSC_VER
namespace detail {template <typename T1, typename T2 = char, typename T3 = char, typename T4 = char, typename T5 = char, typename T6 = char, typename T7 = char>class AlignerImpl { T1 t1; T2 t2; T3 t3; T4 t4; T5 t5; T6 t6; T7 t7;
AlignerImpl(); // Never defined or instantiated.
};
template <typename T1, typename T2 = char, typename T3 = char, typename T4 = char, typename T5 = char, typename T6 = char, typename T7 = 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)];};} // 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 four 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 seven types can
/// be added at the cost of more boiler plate.
template <typename T1, typename T2 = char, typename T3 = char, typename T4 = char, typename T5 = char, typename T6 = char, typename T7 = char>struct AlignedCharArrayUnion : llvm::AlignedCharArray< AlignOf<detail::AlignerImpl<T1, T2, T3, T4, T5, T6, T7> >::Alignment, sizeof(detail::SizerImpl<T1, T2, T3, T4, T5, T6, T7>)> {};} // end namespace llvm
#endif
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