1*4bdff4beSrobert //===----------------------------------------------------------------------===// 2*4bdff4beSrobert // 3*4bdff4beSrobert // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4*4bdff4beSrobert // See https://llvm.org/LICENSE.txt for license information. 5*4bdff4beSrobert // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6*4bdff4beSrobert // 7*4bdff4beSrobert //===----------------------------------------------------------------------===// 8*4bdff4beSrobert 9*4bdff4beSrobert #ifndef _LIBCPP___RANDOM_LOG2_H 10*4bdff4beSrobert #define _LIBCPP___RANDOM_LOG2_H 11*4bdff4beSrobert 12*4bdff4beSrobert #include <__config> 13*4bdff4beSrobert #include <cstddef> 14*4bdff4beSrobert #include <type_traits> 15*4bdff4beSrobert 16*4bdff4beSrobert #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 17*4bdff4beSrobert # pragma GCC system_header 18*4bdff4beSrobert #endif 19*4bdff4beSrobert 20*4bdff4beSrobert _LIBCPP_BEGIN_NAMESPACE_STD 21*4bdff4beSrobert 22*4bdff4beSrobert template <class _UIntType, _UIntType _Xp, size_t _Rp> 23*4bdff4beSrobert struct __log2_imp; 24*4bdff4beSrobert 25*4bdff4beSrobert template <unsigned long long _Xp, size_t _Rp> 26*4bdff4beSrobert struct __log2_imp<unsigned long long, _Xp, _Rp> 27*4bdff4beSrobert { 28*4bdff4beSrobert static const size_t value = _Xp & ((unsigned long long)(1) << _Rp) ? _Rp 29*4bdff4beSrobert : __log2_imp<unsigned long long, _Xp, _Rp - 1>::value; 30*4bdff4beSrobert }; 31*4bdff4beSrobert 32*4bdff4beSrobert template <unsigned long long _Xp> 33*4bdff4beSrobert struct __log2_imp<unsigned long long, _Xp, 0> 34*4bdff4beSrobert { 35*4bdff4beSrobert static const size_t value = 0; 36*4bdff4beSrobert }; 37*4bdff4beSrobert 38*4bdff4beSrobert template <size_t _Rp> 39*4bdff4beSrobert struct __log2_imp<unsigned long long, 0, _Rp> 40*4bdff4beSrobert { 41*4bdff4beSrobert static const size_t value = _Rp + 1; 42*4bdff4beSrobert }; 43*4bdff4beSrobert 44*4bdff4beSrobert #ifndef _LIBCPP_HAS_NO_INT128 45*4bdff4beSrobert 46*4bdff4beSrobert template <__uint128_t _Xp, size_t _Rp> 47*4bdff4beSrobert struct __log2_imp<__uint128_t, _Xp, _Rp> 48*4bdff4beSrobert { 49*4bdff4beSrobert static const size_t value = (_Xp >> 64) 50*4bdff4beSrobert ? (64 + __log2_imp<unsigned long long, (_Xp >> 64), 63>::value) 51*4bdff4beSrobert : __log2_imp<unsigned long long, _Xp, 63>::value; 52*4bdff4beSrobert }; 53*4bdff4beSrobert 54*4bdff4beSrobert #endif // _LIBCPP_HAS_NO_INT128 55*4bdff4beSrobert 56*4bdff4beSrobert template <class _UIntType, _UIntType _Xp> 57*4bdff4beSrobert struct __log2 58*4bdff4beSrobert { 59*4bdff4beSrobert static const size_t value = __log2_imp< 60*4bdff4beSrobert #ifndef _LIBCPP_HAS_NO_INT128 61*4bdff4beSrobert __conditional_t<sizeof(_UIntType) <= sizeof(unsigned long long), unsigned long long, __uint128_t>, 62*4bdff4beSrobert #else 63*4bdff4beSrobert unsigned long long, 64*4bdff4beSrobert #endif // _LIBCPP_HAS_NO_INT128 65*4bdff4beSrobert _Xp, 66*4bdff4beSrobert sizeof(_UIntType) * __CHAR_BIT__ - 1>::value; 67*4bdff4beSrobert }; 68*4bdff4beSrobert 69*4bdff4beSrobert _LIBCPP_END_NAMESPACE_STD 70*4bdff4beSrobert 71*4bdff4beSrobert #endif // _LIBCPP___RANDOM_LOG2_H 72