blob: 2f5b5591dc3f5f20c3eeaf0d6343b15444c16123 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
|
//===----------------------------------------------------------------------===//
//
// 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___CXX03___BIT_COUNTR_H
#define _LIBCPP___CXX03___BIT_COUNTR_H
#include <__cxx03/__bit/rotate.h>
#include <__cxx03/__config>
#include <__cxx03/limits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__cxx03/__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI int __libcpp_ctz(unsigned __x) _NOEXCEPT { return __builtin_ctz(__x); }
_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI int __libcpp_ctz(unsigned long __x) _NOEXCEPT {
return __builtin_ctzl(__x);
}
_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI int __libcpp_ctz(unsigned long long __x) _NOEXCEPT {
return __builtin_ctzll(__x);
}
template <class _Tp>
_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI 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)
}
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___CXX03___BIT_COUNTR_H
|
