1*bdd1243dSDimitry Andric //===----------------------------------------------------------------------===// 2*bdd1243dSDimitry Andric // 3*bdd1243dSDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4*bdd1243dSDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 5*bdd1243dSDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6*bdd1243dSDimitry Andric // 7*bdd1243dSDimitry Andric //===----------------------------------------------------------------------===// 8*bdd1243dSDimitry Andric 9*bdd1243dSDimitry Andric #ifndef _LIBCPP___BIT_BIT_LOG2_H 10*bdd1243dSDimitry Andric #define _LIBCPP___BIT_BIT_LOG2_H 11*bdd1243dSDimitry Andric 12*bdd1243dSDimitry Andric #include <__bit/countl.h> 13*bdd1243dSDimitry Andric #include <__concepts/arithmetic.h> 14*bdd1243dSDimitry Andric #include <__config> 15*bdd1243dSDimitry Andric #include <limits> 16*bdd1243dSDimitry Andric 17*bdd1243dSDimitry Andric #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 18*bdd1243dSDimitry Andric # pragma GCC system_header 19*bdd1243dSDimitry Andric #endif 20*bdd1243dSDimitry Andric 21*bdd1243dSDimitry Andric _LIBCPP_BEGIN_NAMESPACE_STD 22*bdd1243dSDimitry Andric 23*bdd1243dSDimitry Andric #if _LIBCPP_STD_VER >= 20 24*bdd1243dSDimitry Andric 25*bdd1243dSDimitry Andric template <__libcpp_unsigned_integer _Tp> __bit_log2(_Tp __t)26*bdd1243dSDimitry Andric_LIBCPP_HIDE_FROM_ABI constexpr _Tp __bit_log2(_Tp __t) noexcept { 27*bdd1243dSDimitry Andric return numeric_limits<_Tp>::digits - 1 - std::countl_zero(__t); 28*bdd1243dSDimitry Andric } 29*bdd1243dSDimitry Andric 30*bdd1243dSDimitry Andric #endif // _LIBCPP_STD_VER >= 20 31*bdd1243dSDimitry Andric 32*bdd1243dSDimitry Andric _LIBCPP_END_NAMESPACE_STD 33*bdd1243dSDimitry Andric 34*bdd1243dSDimitry Andric #endif // _LIBCPP___BIT_BIT_LOG2_H 35