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[libc++] Replace __libcpp_popcount by __builtin_popcountg (#133937)

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`__libcpp_popcount` was previously used as a fallback for `__builtin_popcountg` to ensure compatibility with older compilers (Clang 18 and earlier), as `__builtin_popcountg` became available in Clang 19. Now that support for Clang 18 has been officially dropped in #130142, we can now safely  replace all instances of `__libcpp_popcount` with `__builtin_popcountg` and eliminate the fallback logic.
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Peng Liu 2025-04-13 08:40:21 -04:00 committed by GitHub
parent 5550d30228
commit 703cfe745b
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GPG Key ID: B5690EEEBB952194
2 changed files with 1 additions and 44 deletions
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43
libcxx/include/__bit/popcount.h
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@ -6,9 +6,6 @@
//
//===----------------------------------------------------------------------===//
// TODO: __builtin_popcountg is available since Clang 19 and GCC 14. When support for older versions is dropped, we can
// refactor this code to exclusively use __builtin_popcountg.
#ifndef _LIBCPP___BIT_POPCOUNT_H
#define _LIBCPP___BIT_POPCOUNT_H
@ -27,50 +24,10 @@ _LIBCPP_PUSH_MACROS
_LIBCPP_BEGIN_NAMESPACE_STD
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_popcount(unsigned __x) _NOEXCEPT {
return __builtin_popcount(__x);
}
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_popcount(unsigned long __x) _NOEXCEPT {
return __builtin_popcountl(__x);
}
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_popcount(unsigned long long __x) _NOEXCEPT {
return __builtin_popcountll(__x);
}
template <class _Tp>
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __popcount_impl(_Tp __t) _NOEXCEPT {
if _LIBCPP_CONSTEXPR (sizeof(_Tp) <= sizeof(unsigned int)) {
return std::__libcpp_popcount(static_cast<unsigned int>(__t));
} else if _LIBCPP_CONSTEXPR (sizeof(_Tp) <= sizeof(unsigned long)) {
return std::__libcpp_popcount(static_cast<unsigned long>(__t));
} else if _LIBCPP_CONSTEXPR (sizeof(_Tp) <= sizeof(unsigned long long)) {
return std::__libcpp_popcount(static_cast<unsigned long long>(__t));
} else {
#if _LIBCPP_STD_VER == 11
return __t != 0 ? std::__libcpp_popcount(static_cast<unsigned long long>(__t)) +
std::__popcount_impl<_Tp>(__t >> numeric_limits<unsigned long long>::digits)
: 0;
#else
int __ret = 0;
while (__t != 0) {
__ret += std::__libcpp_popcount(static_cast<unsigned long long>(__t));
__t >>= std::numeric_limits<unsigned long long>::digits;
}
return __ret;
#endif
}
}
template <class _Tp>
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __popcount(_Tp __t) _NOEXCEPT {
static_assert(is_unsigned<_Tp>::value, "__popcount only works with unsigned types");
#if __has_builtin(__builtin_popcountg) // TODO (LLVM 21): This can be dropped once we only support Clang >= 19.
return __builtin_popcountg(__t);
#else
return std::__popcount_impl(__t);
#endif
}
#if _LIBCPP_STD_VER >= 20

2
libcxx/include/__stop_token/atomic_unique_lock.h
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@ -28,7 +28,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
// and LockedBit is the value of State when the lock bit is set, e.g 1 << 2
template <class _State, _State _LockedBit>
class _LIBCPP_AVAILABILITY_SYNC __atomic_unique_lock {
static_assert(std::__libcpp_popcount(static_cast<unsigned long long>(_LockedBit)) == 1,
static_assert(std::__popcount(static_cast<unsigned long long>(_LockedBit)) == 1,
"LockedBit must be an integer where only one bit is set");
std::atomic<_State>& __state_;