1//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___ALGORITHM_HALF_POSITIVE_H
10#define _LIBCPP___ALGORITHM_HALF_POSITIVE_H
11
12#include <__config>
13#include <__type_traits/enable_if.h>
14#include <__type_traits/is_integral.h>
15#include <__type_traits/make_unsigned.h>
16
17#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
18# pragma GCC system_header
19#endif
20
21_LIBCPP_BEGIN_NAMESPACE_STD
22
23// Perform division by two quickly for positive integers (llvm.org/PR39129)
24
25template <typename _Integral, __enable_if_t<is_integral<_Integral>::value, int> = 0>
26_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Integral __half_positive(_Integral __value) {
27 return static_cast<_Integral>(static_cast<__make_unsigned_t<_Integral> >(__value) / 2);
28}
29
30template <typename _Tp, __enable_if_t<!is_integral<_Tp>::value, int> = 0>
31_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Tp __half_positive(_Tp __value) {
32 return __value / 2;
33}
34
35_LIBCPP_END_NAMESPACE_STD
36
37#endif // _LIBCPP___ALGORITHM_HALF_POSITIVE_H
38