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 
25 template <typename _Integral>
26 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
27 typename enable_if
28 <
29     is_integral<_Integral>::value,
30     _Integral
31 >::type
32 __half_positive(_Integral __value)
33 {
34     return static_cast<_Integral>(static_cast<__make_unsigned_t<_Integral> >(__value) / 2);
35 }
36 
37 template <typename _Tp>
38 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
39 typename enable_if
40 <
41     !is_integral<_Tp>::value,
42     _Tp
43 >::type
44 __half_positive(_Tp __value)
45 {
46     return __value / 2;
47 }
48 
49 _LIBCPP_END_NAMESPACE_STD
50 
51 #endif // _LIBCPP___ALGORITHM_HALF_POSITIVE_H
52