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_PUSH_MACROS 20 #include <__undef_macros> 21 22 _LIBCPP_BEGIN_NAMESPACE_STD 23 24 // Perform division by two quickly for positive integers (llvm.org/PR39129) 25 26 template <typename _Integral> 27 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 28 typename enable_if 29 < 30 is_integral<_Integral>::value, 31 _Integral 32 >::type 33 __half_positive(_Integral __value) 34 { 35 return static_cast<_Integral>(static_cast<typename make_unsigned<_Integral>::type>(__value) / 2); 36 } 37 38 template <typename _Tp> 39 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 40 typename enable_if 41 < 42 !is_integral<_Tp>::value, 43 _Tp 44 >::type 45 __half_positive(_Tp __value) 46 { 47 return __value / 2; 48 } 49 50 _LIBCPP_END_NAMESPACE_STD 51 52 _LIBCPP_POP_MACROS 53 54 #endif // _LIBCPP___ALGORITHM_HALF_POSITIVE_H 55