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> 14 15 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 16 # pragma GCC system_header 17 #endif 18 19 _LIBCPP_BEGIN_NAMESPACE_STD 20 21 // Perform division by two quickly for positive integers (llvm.org/PR39129) 22 23 template <typename _Integral> 24 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 25 typename enable_if 26 < 27 is_integral<_Integral>::value, 28 _Integral 29 >::type 30 __half_positive(_Integral __value) 31 { 32 return static_cast<_Integral>(static_cast<typename make_unsigned<_Integral>::type>(__value) / 2); 33 } 34 35 template <typename _Tp> 36 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 37 typename enable_if 38 < 39 !is_integral<_Tp>::value, 40 _Tp 41 >::type 42 __half_positive(_Tp __value) 43 { 44 return __value / 2; 45 } 46 47 _LIBCPP_END_NAMESPACE_STD 48 49 #endif // _LIBCPP___ALGORITHM_HALF_POSITIVE_H 50