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[libc++] Refactor atomic_{unsigned,signed}_lock_free #73041

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Merged
merged 1 commit into from
Nov 22, 2023
+31 −28
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[libc++] Refactor atomic_{unsigned,signed}_lock_free #73041

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51 changes: 23 additions & 28 deletions libcxx/include/__atomic/aliases.h
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
#include <__atomic/is_always_lock_free.h>
#include <__config>
#include <__type_traits/conditional.h>
#include <__type_traits/make_unsigned.h>
#include <cstddef>
#include <cstdint>
#include <cstdlib>
Expand Down Expand Up @@ -80,36 +81,30 @@ using atomic_ptrdiff_t = atomic<ptrdiff_t>;
using atomic_intmax_t = atomic<intmax_t>;
using atomic_uintmax_t = atomic<uintmax_t>;

// atomic_*_lock_free : prefer the contention type most highly, then the largest lock-free type
// C++20 atomic_{signed,unsigned}_lock_free: prefer the contention type most highly, then the largest lock-free type
#if _LIBCPP_STD_VER >= 20
# if ATOMIC_LLONG_LOCK_FREE == 2
using __largest_lock_free_type = long long;
# elif ATOMIC_INT_LOCK_FREE == 2
using __largest_lock_free_type = int;
# elif ATOMIC_SHORT_LOCK_FREE == 2
using __largest_lock_free_type = short;
# elif ATOMIC_CHAR_LOCK_FREE == 2
using __largest_lock_free_type = char;
# else
# define _LIBCPP_NO_LOCK_FREE_TYPES // There are no lockfree types (this can happen in freestanding)
# endif

#if _LIBCPP_STD_VER >= 17
# define _LIBCPP_CONTENTION_LOCK_FREE ::std::__libcpp_is_always_lock_free<__cxx_contention_t>::__value
#else
# define _LIBCPP_CONTENTION_LOCK_FREE false
#endif

#if ATOMIC_LLONG_LOCK_FREE == 2
using __libcpp_signed_lock_free = __conditional_t<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, long long>;
using __libcpp_unsigned_lock_free =
__conditional_t<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, unsigned long long>;
#elif ATOMIC_INT_LOCK_FREE == 2
using __libcpp_signed_lock_free = __conditional_t<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, int>;
using __libcpp_unsigned_lock_free = __conditional_t<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, unsigned int>;
#elif ATOMIC_SHORT_LOCK_FREE == 2
using __libcpp_signed_lock_free = __conditional_t<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, short>;
using __libcpp_unsigned_lock_free = __conditional_t<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, unsigned short>;
#elif ATOMIC_CHAR_LOCK_FREE == 2
using __libcpp_signed_lock_free = __conditional_t<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, char>;
using __libcpp_unsigned_lock_free = __conditional_t<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, unsigned char>;
#else
// No signed/unsigned lock-free types
# define _LIBCPP_NO_LOCK_FREE_TYPES
#endif
# ifndef _LIBCPP_NO_LOCK_FREE_TYPES
using __contention_t_or_largest =
__conditional_t<__libcpp_is_always_lock_free<__cxx_contention_t>::__value,
__cxx_contention_t,
__largest_lock_free_type>;

#if !defined(_LIBCPP_NO_LOCK_FREE_TYPES)
using atomic_signed_lock_free = atomic<__libcpp_signed_lock_free>;
using atomic_unsigned_lock_free = atomic<__libcpp_unsigned_lock_free>;
#endif
using atomic_signed_lock_free = atomic<__contention_t_or_largest>;
using atomic_unsigned_lock_free = atomic<make_unsigned_t<__contention_t_or_largest>>;
# endif // !_LIBCPP_NO_LOCK_FREE_TYPES
#endif // C++20

_LIBCPP_END_NAMESPACE_STD

Expand Down
3 changes: 3 additions & 0 deletions libcxx/include/atomic
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Original file line number Diff line number Diff line change
Expand Up @@ -448,6 +448,9 @@ typedef atomic<ptrdiff_t> atomic_ptrdiff_t;
typedef atomic<intmax_t> atomic_intmax_t;
typedef atomic<uintmax_t> atomic_uintmax_t;

typedef see-below atomic_signed_lock_free; // since C++20
typedef see-below atomic_unsigned_lock_free; // since C++20

// flag type and operations

typedef struct atomic_flag
Expand Down
5 changes: 5 additions & 0 deletions libcxx/test/std/atomics/types.pass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -175,7 +175,12 @@ int main(int, char**)

#if TEST_STD_VER >= 20
test<std::atomic_signed_lock_free::value_type>();
static_assert(std::is_signed_v<std::atomic_signed_lock_free::value_type>);
static_assert(std::is_integral_v<std::atomic_signed_lock_free::value_type>);

test<std::atomic_unsigned_lock_free::value_type>();
static_assert(std::is_unsigned_v<std::atomic_unsigned_lock_free::value_type>);
static_assert(std::is_integral_v<std::atomic_unsigned_lock_free::value_type>);
/*
test<std::shared_ptr<int>>();
*/
Expand Down