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 <__config>
14#include <__type_traits/integer_traits.h>
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
23template <class _Tp>
24_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp __bit_log2(_Tp __t) _NOEXCEPT {
25 static_assert(__is_unsigned_integer_v<_Tp>, "__bit_log2 requires an unsigned integer type");
26 return numeric_limits<_Tp>::digits - 1 - std::__countl_zero(__t);
27}
28
29_LIBCPP_END_NAMESPACE_STD
30
31#endif // _LIBCPP___BIT_BIT_LOG2_H
32