//===----------------------------------------------------------------------===//
//
// Part of libcu++, the C++ Standard Library for your entire system,
// under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCUDACXX___BIT_COUNTL_H
#define _LIBCUDACXX___BIT_COUNTL_H

#include <cuda/std/detail/__config>

#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
#  pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
#  pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
#  pragma system_header
#endif // no system header

#include <cuda/std/__bit/bit_cast.h>
#include <cuda/std/__bit/clz.h>
#include <cuda/std/__concepts/concept_macros.h>
#include <cuda/std/__type_traits/conditional.h>
#include <cuda/std/__type_traits/is_constant_evaluated.h>
#include <cuda/std/__type_traits/is_unsigned_integer.h>
#include <cuda/std/cstdint>
#include <cuda/std/limits>

_LIBCUDACXX_BEGIN_NAMESPACE_STD

_CCCL_TEMPLATE(class _Tp)
_CCCL_REQUIRES(_CCCL_TRAIT(_CUDA_VSTD::__cccl_is_unsigned_integer, _Tp) _CCCL_AND(sizeof(_Tp) <= sizeof(uint64_t)))
_LIBCUDACXX_HIDE_FROM_ABI constexpr int __countl_zero(_Tp __t) noexcept
{
  using _Sp                    = _If<sizeof(_Tp) <= sizeof(uint32_t), uint32_t, uint64_t>;
  constexpr auto __digits_diff = numeric_limits<_Sp>::digits - numeric_limits<_Tp>::digits;
  return _CUDA_VSTD::__cccl_clz(static_cast<_Sp>(__t)) - __digits_diff;
}

_CCCL_TEMPLATE(class _Tp)
_CCCL_REQUIRES(_CCCL_TRAIT(_CUDA_VSTD::__cccl_is_unsigned_integer, _Tp) _CCCL_AND(sizeof(_Tp) > sizeof(uint64_t)))
_LIBCUDACXX_HIDE_FROM_ABI constexpr int __countl_zero(_Tp __t) noexcept
{
  constexpr int _Ratio = sizeof(_Tp) / sizeof(uint64_t);
  for (int __i = _Ratio - 1; __i >= 0; --__i)
  {
    auto __value64 = static_cast<uint64_t>(__t >> (__i * numeric_limits<uint64_t>::digits));
    if (static_cast<uint64_t>(__value64))
    {
      return _CUDA_VSTD::__countl_zero(__value64) + (_Ratio - 1 - __i) * numeric_limits<uint64_t>::digits;
    }
  }
  return numeric_limits<_Tp>::digits;
}

_CCCL_TEMPLATE(class _Tp)
_CCCL_REQUIRES(_CCCL_TRAIT(_CUDA_VSTD::__cccl_is_unsigned_integer, _Tp))
_CCCL_NODISCARD _LIBCUDACXX_HIDE_FROM_ABI constexpr int countl_zero(_Tp __t) noexcept
{
  auto __ret = _CUDA_VSTD::__countl_zero(static_cast<_Tp>(__t));
  _CCCL_ASSUME(__ret >= 0 && __ret <= numeric_limits<_Tp>::digits);
  return __ret;
}

_CCCL_TEMPLATE(class _Tp)
_CCCL_REQUIRES(_CCCL_TRAIT(_CUDA_VSTD::__cccl_is_unsigned_integer, _Tp))
_CCCL_NODISCARD _LIBCUDACXX_HIDE_FROM_ABI constexpr int countl_one(_Tp __t) noexcept
{
  return _CUDA_VSTD::countl_zero(static_cast<_Tp>(~__t));
}

_LIBCUDACXX_END_NAMESPACE_STD

#endif // _LIBCUDACXX___BIT_COUNTL_H