v1/__algorithm/half_positive.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___ALGORITHM_HALF_POSITIVE_H
0010 #define _LIBCPP___ALGORITHM_HALF_POSITIVE_H
0011
0012 #include <__config>
0013 #include <__type_traits/enable_if.h>
0014 #include <__type_traits/is_integral.h>
0015 #include <__type_traits/make_unsigned.h>
0016
0017 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0018 #  pragma GCC system_header
0019 #endif
0020
0021 _LIBCPP_BEGIN_NAMESPACE_STD
0022
0023 // Perform division by two quickly for positive integers (llvm.org/PR39129)
0024
0025 template <typename _Integral, __enable_if_t<is_integral<_Integral>::value, int> = 0>
0026 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Integral __half_positive(_Integral __value) {
0027   return static_cast<_Integral>(static_cast<__make_unsigned_t<_Integral> >(__value) / 2);
0028 }
0029
0030 template <typename _Tp, __enable_if_t<!is_integral<_Tp>::value, int> = 0>
0031 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Tp __half_positive(_Tp __value) {
0032   return __value / 2;
0033 }
0034
0035 _LIBCPP_END_NAMESPACE_STD
0036
0037 #endif // _LIBCPP___ALGORITHM_HALF_POSITIVE_H