mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 11:37:35 +00:00
84 lines
2.8 KiB
C++
84 lines
2.8 KiB
C++
//===----------------------------------------------------------------------===//
|
|
//
|
|
// Part of the LLVM Project, 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
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
// TODO: __builtin_ctzg is available since Clang 19 and GCC 14. When support for older versions is dropped, we can
|
|
// refactor this code to exclusively use __builtin_ctzg.
|
|
|
|
#ifndef _LIBCPP___BIT_COUNTR_H
|
|
#define _LIBCPP___BIT_COUNTR_H
|
|
|
|
#include <__bit/rotate.h>
|
|
#include <__concepts/arithmetic.h>
|
|
#include <__config>
|
|
#include <limits>
|
|
|
|
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
|
|
# pragma GCC system_header
|
|
#endif
|
|
|
|
_LIBCPP_PUSH_MACROS
|
|
#include <__undef_macros>
|
|
|
|
_LIBCPP_BEGIN_NAMESPACE_STD
|
|
|
|
_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_ctz(unsigned __x) _NOEXCEPT {
|
|
return __builtin_ctz(__x);
|
|
}
|
|
|
|
_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_ctz(unsigned long __x) _NOEXCEPT {
|
|
return __builtin_ctzl(__x);
|
|
}
|
|
|
|
_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_ctz(unsigned long long __x) _NOEXCEPT {
|
|
return __builtin_ctzll(__x);
|
|
}
|
|
|
|
template <class _Tp>
|
|
_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 int __countr_zero(_Tp __t) _NOEXCEPT {
|
|
#if __has_builtin(__builtin_ctzg)
|
|
return __builtin_ctzg(__t, numeric_limits<_Tp>::digits);
|
|
#else // __has_builtin(__builtin_ctzg)
|
|
if (__t == 0)
|
|
return numeric_limits<_Tp>::digits;
|
|
if (sizeof(_Tp) <= sizeof(unsigned int))
|
|
return std::__libcpp_ctz(static_cast<unsigned int>(__t));
|
|
else if (sizeof(_Tp) <= sizeof(unsigned long))
|
|
return std::__libcpp_ctz(static_cast<unsigned long>(__t));
|
|
else if (sizeof(_Tp) <= sizeof(unsigned long long))
|
|
return std::__libcpp_ctz(static_cast<unsigned long long>(__t));
|
|
else {
|
|
int __ret = 0;
|
|
const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
|
|
while (static_cast<unsigned long long>(__t) == 0uLL) {
|
|
__ret += __ulldigits;
|
|
__t >>= __ulldigits;
|
|
}
|
|
return __ret + std::__libcpp_ctz(static_cast<unsigned long long>(__t));
|
|
}
|
|
#endif // __has_builtin(__builtin_ctzg)
|
|
}
|
|
|
|
#if _LIBCPP_STD_VER >= 20
|
|
|
|
template <__libcpp_unsigned_integer _Tp>
|
|
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr int countr_zero(_Tp __t) noexcept {
|
|
return std::__countr_zero(__t);
|
|
}
|
|
|
|
template <__libcpp_unsigned_integer _Tp>
|
|
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr int countr_one(_Tp __t) noexcept {
|
|
return __t != numeric_limits<_Tp>::max() ? std::countr_zero(static_cast<_Tp>(~__t)) : numeric_limits<_Tp>::digits;
|
|
}
|
|
|
|
#endif // _LIBCPP_STD_VER >= 20
|
|
|
|
_LIBCPP_END_NAMESPACE_STD
|
|
|
|
_LIBCPP_POP_MACROS
|
|
|
|
#endif // _LIBCPP___BIT_COUNTR_H
|