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/*
* Copyright 2017 NVIDIA Corporation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*! \file alignment.h
* \brief Type-alignment utilities.
*/
#pragma once
#include <thrust/detail/config.h>
#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
# pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
# pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
# pragma system_header
#endif // no system header
#include <thrust/detail/type_traits.h> // For `integral_constant`.
#include <cstddef> // For `std::size_t` and `std::max_align_t`.
#if THRUST_CPP_DIALECT >= 2011
#include <type_traits> // For `std::alignment_of`.
#endif
THRUST_NAMESPACE_BEGIN
namespace detail
{
/// \p THRUST_ALIGNOF is a macro that takes a single type-id as a parameter,
/// and returns the alignment requirement of the type in bytes.
///
/// It is an approximation of C++11's `alignof` operator.
///
/// Note: MSVC does not allow the builtin used to implement this to be placed
/// inside of a `__declspec(align(#))` attribute. As a workaround, you can
/// assign the result of \p THRUST_ALIGNOF to a variable and pass the variable
/// as the argument to `__declspec(align(#))`.
#if THRUST_CPP_DIALECT >= 2011
#define THRUST_ALIGNOF(x) alignof(x)
#else
#define THRUST_ALIGNOF(x) __alignof(x)
#endif
/// \p alignment_of provides the member constant `value` which is equal to the
/// alignment requirement of the type `T`, as if obtained by a C++11 `alignof`
/// expression.
///
/// It is an implementation of C++11's \p std::alignment_of.
#if THRUST_CPP_DIALECT >= 2011
template <typename T>
using alignment_of = std::alignment_of<T>;
#else
template <typename T>
struct alignment_of;
template <typename T, std::size_t size_diff>
struct alignment_of_helper
{
static const std::size_t value =
integral_constant<std::size_t, size_diff>::value;
};
template <typename T>
struct alignment_of_helper<T, 0>
{
static const std::size_t value = alignment_of<T>::value;
};
template <typename T>
struct alignment_of
{
private:
struct impl
{
T x;
char c;
};
public:
static const std::size_t value =
alignment_of_helper<impl, sizeof(impl) - sizeof(T)>::value;
};
#endif
/// \p aligned_type provides the nested type `type`, which is a trivial
/// type whose alignment requirement is a divisor of `Align`.
///
/// The behavior is undefined if `Align` is not a power of 2.
template <std::size_t Align>
struct aligned_type;
#if THRUST_CPP_DIALECT >= 2011 \
&& (THRUST_HOST_COMPILER == THRUST_HOST_COMPILER_GCC) \
&& (THRUST_GCC_VERSION >= 40800)
// C++11 implementation, excluding GCC 4.7, which doesn't have `alignas`.
template <std::size_t Align>
struct aligned_type
{
struct alignas(Align) type {};
};
#elif (THRUST_HOST_COMPILER == THRUST_HOST_COMPILER_MSVC) \
|| ( (THRUST_HOST_COMPILER == THRUST_HOST_COMPILER_GCC) \
&& (THRUST_GCC_VERSION < 40600))
// C++03 implementation for MSVC and GCC <= 4.5.
//
// We have to implement `aligned_type` with specializations for MSVC
// and GCC 4.2.x and older because they require literals as arguments to
// their alignment attribute.
#if (THRUST_HOST_COMPILER == THRUST_HOST_COMPILER_MSVC)
// MSVC implementation.
#define THRUST_DEFINE_ALIGNED_TYPE_SPECIALIZATION(X) \
template <> \
struct aligned_type<X> \
{ \
__declspec(align(X)) struct type {}; \
}; \
/**/
#else
// GCC <= 4.2 implementation.
#define THRUST_DEFINE_ALIGNED_TYPE_SPECIALIZATION(X) \
template <> \
struct aligned_type<X> \
{ \
struct type {} __attribute__((aligned(X))); \
}; \
/**/
#endif
THRUST_DEFINE_ALIGNED_TYPE_SPECIALIZATION(1);
THRUST_DEFINE_ALIGNED_TYPE_SPECIALIZATION(2);
THRUST_DEFINE_ALIGNED_TYPE_SPECIALIZATION(4);
THRUST_DEFINE_ALIGNED_TYPE_SPECIALIZATION(8);
THRUST_DEFINE_ALIGNED_TYPE_SPECIALIZATION(16);
THRUST_DEFINE_ALIGNED_TYPE_SPECIALIZATION(32);
THRUST_DEFINE_ALIGNED_TYPE_SPECIALIZATION(64);
THRUST_DEFINE_ALIGNED_TYPE_SPECIALIZATION(128);
#undef THRUST_DEFINE_ALIGNED_TYPE_SPECIALIZATION
#else
// C++03 implementation for GCC > 4.5, Clang, PGI, ICPC, and xlC.
template <std::size_t Align>
struct aligned_type
{
struct type {} __attribute__((aligned(Align)));
};
#endif
/// \p max_align_t is a trivial type whose alignment requirement is at least as
/// strict (as large) as that of every scalar type.
///
/// It is an implementation of C++11's \p std::max_align_t.
#if THRUST_CPP_DIALECT >= 2011 \
&& (THRUST_HOST_COMPILER == THRUST_HOST_COMPILER_GCC) \
&& (THRUST_GCC_VERSION >= 40900)
// GCC 4.7 and 4.8 don't have `std::max_align_t`.
using max_align_t = std::max_align_t;
#else
union max_align_t
{
// These cannot be private because C++03 POD types cannot have private
// data members.
char c;
short s;
int i;
long l;
float f;
double d;
long long ll;
long double ld;
void* p;
};
#endif
/// \p aligned_reinterpret_cast `reinterpret_cast`s \p u of type \p U to `void*`
/// and then `reinterpret_cast`s the result to \p T. The indirection through
/// `void*` suppresses compiler warnings when the alignment requirement of \p *u
/// is less than the alignment requirement of \p *t. The caller of
/// \p aligned_reinterpret_cast is responsible for ensuring that the alignment
/// requirements are actually satisified.
template <typename T, typename U>
__host__ __device__
T aligned_reinterpret_cast(U u)
{
return reinterpret_cast<T>(reinterpret_cast<void*>(u));
}
__host__ __device__
inline std::size_t aligned_storage_size(std::size_t n, std::size_t align)
{
return ((n + align - 1) / align) * align;
}
} // end namespace detail
THRUST_NAMESPACE_END
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