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___BIT_BIT_LOG2_H 10 #define _LIBCPP___BIT_BIT_LOG2_H 11 12 #include <__bit/countl.h> 13 #include <__concepts/arithmetic.h> 14 #include <__config> 15 #include <limits> 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 #if _LIBCPP_STD_VER >= 20 24 25 template <__libcpp_unsigned_integer _Tp> 26 _LIBCPP_HIDE_FROM_ABI constexpr _Tp __bit_log2(_Tp __t) noexcept { 27 return numeric_limits<_Tp>::digits - 1 - std::countl_zero(__t); 28 } 29 30 #endif // _LIBCPP_STD_VER >= 20 31 32 _LIBCPP_END_NAMESPACE_STD 33 34 #endif // _LIBCPP___BIT_BIT_LOG2_H 35