__cxx03/__bit/bit_log2.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___CXX03___BIT_BIT_LOG2_H
0010 #define _LIBCPP___CXX03___BIT_BIT_LOG2_H
0011
0012 #include <__cxx03/__bit/countl.h>
0013 #include <__cxx03/__concepts/arithmetic.h>
0014 #include <__cxx03/__config>
0015 #include <__cxx03/limits>
0016
0017 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0018 #  pragma GCC system_header
0019 #endif
0020
0021 _LIBCPP_BEGIN_NAMESPACE_STD
0022
0023 #if _LIBCPP_STD_VER >= 20
0024
0025 template <__libcpp_unsigned_integer _Tp>
0026 _LIBCPP_HIDE_FROM_ABI constexpr _Tp __bit_log2(_Tp __t) noexcept {
0027   return numeric_limits<_Tp>::digits - 1 - std::countl_zero(__t);
0028 }
0029
0030 #endif // _LIBCPP_STD_VER >= 20
0031
0032 _LIBCPP_END_NAMESPACE_STD
0033
0034 #endif // _LIBCPP___CXX03___BIT_BIT_LOG2_H