libcxx/include/__cxx03/__memory/assume_aligned.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___CXX03___MEMORY_ASSUME_ALIGNED_H
  11 #define _LIBCPP___CXX03___MEMORY_ASSUME_ALIGNED_H
  12
  13 #include <__cxx03/__assert>
  14 #include <__cxx03/__config>
  15 #include <__cxx03/__type_traits/is_constant_evaluated.h>
  16 #include <__cxx03/cstddef>
  17 #include <__cxx03/cstdint>
  18
  19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  20 #  pragma GCC system_header
  21 #endif
  22
  23 _LIBCPP_BEGIN_NAMESPACE_STD
  24
  25 template <size_t _Np, class _Tp>
  26 _LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp* __assume_aligned(_Tp* __ptr) {
  27   static_assert(_Np != 0 && (_Np & (_Np - 1)) == 0, "std::assume_aligned<N>(p) requires N to be a power of two");
  28
  29   if (__libcpp_is_constant_evaluated()) {
  30     (void)__builtin_assume_aligned(__ptr, _Np);
  31     return __ptr;
  32   } else {
  33     _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
  34         reinterpret_cast<uintptr_t>(__ptr) % _Np == 0, "Alignment assumption is violated");
  35     return static_cast<_Tp*>(__builtin_assume_aligned(__ptr, _Np));
  36   }
  37 }
  38
  39 #if _LIBCPP_STD_VER >= 20
  40
  41 template <size_t _Np, class _Tp>
  42 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp* assume_aligned(_Tp* __ptr) {
  43   return std::__assume_aligned<_Np>(__ptr);
  44 }
  45
  46 #endif // _LIBCPP_STD_VER >= 20
  47
  48 _LIBCPP_END_NAMESPACE_STD
  49
  50 #endif // _LIBCPP___CXX03___MEMORY_ASSUME_ALIGNED_H