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| 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 | // TODO: __builtin_ctzg is available since Clang 19 and GCC 14. When support for older versions is dropped, we can |
| 10 | // refactor this code to exclusively use __builtin_ctzg. |
| 11 | |
| 12 | #ifndef _LIBCPP___CXX03___BIT_COUNTR_H |
| 13 | #define _LIBCPP___CXX03___BIT_COUNTR_H |
| 14 | |
| 15 | #include <__cxx03/__bit/rotate.h> |
| 16 | #include <__cxx03/__config> |
| 17 | #include <__cxx03/limits> |
| 18 | |
| 19 | #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| 20 | # pragma GCC system_header |
| 21 | #endif |
| 22 | |
| 23 | _LIBCPP_PUSH_MACROS |
| 24 | #include <__cxx03/__undef_macros> |
| 25 | |
| 26 | _LIBCPP_BEGIN_NAMESPACE_STD |
| 27 | |
| 28 | _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI int __libcpp_ctz(unsigned __x) _NOEXCEPT { return __builtin_ctz(__x); } |
| 29 | |
| 30 | _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI int __libcpp_ctz(unsigned long __x) _NOEXCEPT { |
| 31 | return __builtin_ctzl(__x); |
| 32 | } |
| 33 | |
| 34 | _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI int __libcpp_ctz(unsigned long long __x) _NOEXCEPT { |
| 35 | return __builtin_ctzll(__x); |
| 36 | } |
| 37 | |
| 38 | template <class _Tp> |
| 39 | _LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI int __countr_zero(_Tp __t) _NOEXCEPT { |
| 40 | #if __has_builtin(__builtin_ctzg) |
| 41 | return __builtin_ctzg(__t, numeric_limits<_Tp>::digits); |
| 42 | #else // __has_builtin(__builtin_ctzg) |
| 43 | if (__t == 0) |
| 44 | return numeric_limits<_Tp>::digits; |
| 45 | if (sizeof(_Tp) <= sizeof(unsigned int)) |
| 46 | return std::__libcpp_ctz(static_cast<unsigned int>(__t)); |
| 47 | else if (sizeof(_Tp) <= sizeof(unsigned long)) |
| 48 | return std::__libcpp_ctz(static_cast<unsigned long>(__t)); |
| 49 | else if (sizeof(_Tp) <= sizeof(unsigned long long)) |
| 50 | return std::__libcpp_ctz(static_cast<unsigned long long>(__t)); |
| 51 | else { |
| 52 | int __ret = 0; |
| 53 | const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits; |
| 54 | while (static_cast<unsigned long long>(__t) == 0uLL) { |
| 55 | __ret += __ulldigits; |
| 56 | __t >>= __ulldigits; |
| 57 | } |
| 58 | return __ret + std::__libcpp_ctz(static_cast<unsigned long long>(__t)); |
| 59 | } |
| 60 | #endif // __has_builtin(__builtin_ctzg) |
| 61 | } |
| 62 | |
| 63 | _LIBCPP_END_NAMESPACE_STD |
| 64 | |
| 65 | _LIBCPP_POP_MACROS |
| 66 | |
| 67 | #endif // _LIBCPP___CXX03___BIT_COUNTR_H |
| 68 |
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