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 <__assert> 13 #include <__bit/countl.h> 14 #include <__config> 15 #include <__type_traits/integer_traits.h> 16 #include <limits> 17 18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 19 # pragma GCC system_header 20 #endif 21 22 _LIBCPP_BEGIN_NAMESPACE_STD 23 24 template <class _Tp> __bit_log2(_Tp __t)25_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp __bit_log2(_Tp __t) _NOEXCEPT { 26 static_assert(__is_unsigned_integer_v<_Tp>, "__bit_log2 requires an unsigned integer type"); 27 _LIBCPP_ASSERT_INTERNAL(__t != 0, "logarithm of 0 is undefined"); 28 return numeric_limits<_Tp>::digits - 1 - std::__countl_zero(__t); 29 } 30 31 _LIBCPP_END_NAMESPACE_STD 32 33 #endif // _LIBCPP___BIT_BIT_LOG2_H 34