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Emulate clang atomic built-ins on gcc > 4.7
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gcc 4.7 and above has atomic built-ins which slightly different APIs
from those provided by clang. Add proxy functions that wrap the gcc
built-ins to produce a symbol that is API equivalent to the clang
built-ins. This allows libc++'s atomic library to be used with gcc-4.7
and newer.

Patch contributed by Albert Wong.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@215305 91177308-0d34-0410-b5e6-96231b3b80d8
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@DanAlbert
DanAlbert committed Aug 9, 2014
1 parent ddcbcd6 commit e8b4232
Showing 1 changed file with 252 additions and 1 deletion.
253 changes: 252 additions & 1 deletion include/atomic
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Expand Up @@ -535,7 +535,7 @@ void atomic_signal_fence(memory_order m) noexcept;

_LIBCPP_BEGIN_NAMESPACE_STD

#if !__has_feature(cxx_atomic)
#if !__has_feature(cxx_atomic) && _GNUC_VER < 407
#error <atomic> is not implemented
#else

Expand All @@ -545,6 +545,257 @@ typedef enum memory_order
memory_order_release, memory_order_acq_rel, memory_order_seq_cst
} memory_order;

#if _GNUC_VER >= 407
namespace __gcc_atomic {
template <typename T>
struct __gcc_atomic_t {
__gcc_atomic_t() _NOEXCEPT {}
explicit __gcc_atomic_t(T value) _NOEXCEPT : __a_value(value) {}
T __a_value;
};
#define _Atomic(x) __gcc_atomic::__gcc_atomic_t<x>

template <typename T> T __create();

template <typename __Tp, typename __Td>
typename enable_if<sizeof(__Tp()->__a_value = __create<__Td>()), char>::type
__test_atomic_assignable(int);
template <typename T, typename U>
__two __test_atomic_assignable(...);

template <typename __Tp, typename __Td>
struct __can_assign {
static const bool value =
sizeof(__test_atomic_assignable<__Tp, __Td>(1)) == sizeof(char);
};

static inline constexpr int __to_gcc_order(memory_order __order) {
// Avoid switch statement to make this a constexpr.
return __order == memory_order_relaxed ? __ATOMIC_RELAXED:
(__order == memory_order_acquire ? __ATOMIC_ACQUIRE:
(__order == memory_order_release ? __ATOMIC_RELEASE:
(__order == memory_order_seq_cst ? __ATOMIC_SEQ_CST:
(__order == memory_order_acq_rel ? __ATOMIC_ACQ_REL:
__ATOMIC_CONSUME))));
}

} // namespace __gcc_atomic

template <typename _Tp>
static inline
typename enable_if<
__gcc_atomic::__can_assign<volatile _Atomic(_Tp)*, _Tp>::value>::type
__c11_atomic_init(volatile _Atomic(_Tp)* __a, _Tp __val) {
__a->__a_value = __val;
}

template <typename _Tp>
static inline
typename enable_if<
!__gcc_atomic::__can_assign<volatile _Atomic(_Tp)*, _Tp>::value &&
__gcc_atomic::__can_assign< _Atomic(_Tp)*, _Tp>::value>::type
__c11_atomic_init(volatile _Atomic(_Tp)* __a, _Tp __val) {
// [atomics.types.generic]p1 guarantees _Tp is trivially copyable. Because
// the default operator= in an object is not volatile, a byte-by-byte copy
// is required.
volatile char* to = reinterpret_cast<volatile char*>(&__a->__a_value);
volatile char* end = to + sizeof(_Tp);
char* from = reinterpret_cast<char*>(&__val);
while (to != end) {
*to++ = *from++;
}
}

template <typename _Tp>
static inline void __c11_atomic_init(_Atomic(_Tp)* __a, _Tp __val) {
__a->__a_value = __val;
}

static inline void __c11_atomic_thread_fence(memory_order __order) {
__atomic_thread_fence(__gcc_atomic::__to_gcc_order(__order));
}

static inline void __c11_atomic_signal_fence(memory_order __order) {
__atomic_signal_fence(__gcc_atomic::__to_gcc_order(__order));
}

static inline bool __c11_atomic_is_lock_free(size_t __size) {
return __atomic_is_lock_free(__size, 0);
}

template <typename _Tp>
static inline void __c11_atomic_store(volatile _Atomic(_Tp)* __a, _Tp __val,
memory_order __order) {
return __atomic_store(&__a->__a_value, &__val,
__gcc_atomic::__to_gcc_order(__order));
}

template <typename _Tp>
static inline void __c11_atomic_store(_Atomic(_Tp)* __a, _Tp __val,
memory_order __order) {
return __atomic_store(&__a->__a_value, &__val,
__gcc_atomic::__to_gcc_order(__order));
}

template <typename _Tp>
static inline _Tp __c11_atomic_load(volatile _Atomic(_Tp)* __a,
memory_order __order) {
_Tp __ret;
__atomic_load(&__a->__a_value, &__ret,
__gcc_atomic::__to_gcc_order(__order));
return __ret;
}

template <typename _Tp>
static inline _Tp __c11_atomic_load(_Atomic(_Tp)* __a, memory_order __order) {
_Tp __ret;
__atomic_load(&__a->__a_value, &__ret,
__gcc_atomic::__to_gcc_order(__order));
return __ret;
}

template <typename _Tp>
static inline _Tp __c11_atomic_exchange(volatile _Atomic(_Tp)* __a,
_Tp __value, memory_order __order) {
_Tp __ret;
__atomic_exchange(&__a->__a_value, &__value, &__ret,
__gcc_atomic::__to_gcc_order(__order));
return __ret;
}

template <typename _Tp>
static inline _Tp __c11_atomic_exchange(_Atomic(_Tp)* __a, _Tp __value,
memory_order __order) {
_Tp __ret;
__atomic_exchange(&__a->__a_value, &__value, &__ret,
__gcc_atomic::__to_gcc_order(__order));
return __ret;
}

template <typename _Tp>
static inline bool __c11_atomic_compare_exchange_strong(
volatile _Atomic(_Tp)* __a, _Tp* __expected, _Tp __value,
memory_order __success, memory_order __failure) {
return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
false,
__gcc_atomic::__to_gcc_order(__success),
__gcc_atomic::__to_gcc_order(__failure));
}

template <typename _Tp>
static inline bool __c11_atomic_compare_exchange_strong(
_Atomic(_Tp)* __a, _Tp* __expected, _Tp __value, memory_order __success,
memory_order __failure) {
return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
false,
__gcc_atomic::__to_gcc_order(__success),
__gcc_atomic::__to_gcc_order(__failure));
}

template <typename _Tp>
static inline bool __c11_atomic_compare_exchange_weak(
volatile _Atomic(_Tp)* __a, _Tp* __expected, _Tp __value,
memory_order __success, memory_order __failure) {
return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
true,
__gcc_atomic::__to_gcc_order(__success),
__gcc_atomic::__to_gcc_order(__failure));
}

template <typename _Tp>
static inline bool __c11_atomic_compare_exchange_weak(
_Atomic(_Tp)* __a, _Tp* __expected, _Tp __value, memory_order __success,
memory_order __failure) {
return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
true,
__gcc_atomic::__to_gcc_order(__success),
__gcc_atomic::__to_gcc_order(__failure));
}

template <typename _Tp>
struct __skip_amt { enum {value = 1}; };

template <typename _Tp>
struct __skip_amt<_Tp*> { enum {value = sizeof(_Tp)}; };

// FIXME: Haven't figured out what the spec says about using arrays with
// atomic_fetch_add. Force a failure rather than creating bad behavior.
template <typename _Tp>
struct __skip_amt<_Tp[]> { };
template <typename _Tp, int n>
struct __skip_amt<_Tp[n]> { };

template <typename _Tp, typename _Td>
static inline _Tp __c11_atomic_fetch_add(volatile _Atomic(_Tp)* __a,
_Td __delta, memory_order __order) {
return __atomic_fetch_add(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
__gcc_atomic::__to_gcc_order(__order));
}

template <typename _Tp, typename _Td>
static inline _Tp __c11_atomic_fetch_add(_Atomic(_Tp)* __a, _Td __delta,
memory_order __order) {
return __atomic_fetch_add(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
__gcc_atomic::__to_gcc_order(__order));
}

template <typename _Tp, typename _Td>
static inline _Tp __c11_atomic_fetch_sub(volatile _Atomic(_Tp)* __a,
_Td __delta, memory_order __order) {
return __atomic_fetch_sub(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
__gcc_atomic::__to_gcc_order(__order));
}

template <typename _Tp, typename _Td>
static inline _Tp __c11_atomic_fetch_sub(_Atomic(_Tp)* __a, _Td __delta,
memory_order __order) {
return __atomic_fetch_sub(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
__gcc_atomic::__to_gcc_order(__order));
}

template <typename _Tp>
static inline _Tp __c11_atomic_fetch_and(volatile _Atomic(_Tp)* __a,
_Tp __pattern, memory_order __order) {
return __atomic_fetch_and(&__a->__a_value, __pattern,
__gcc_atomic::__to_gcc_order(__order));
}

template <typename _Tp>
static inline _Tp __c11_atomic_fetch_and(_Atomic(_Tp)* __a,
_Tp __pattern, memory_order __order) {
return __atomic_fetch_and(&__a->__a_value, __pattern,
__gcc_atomic::__to_gcc_order(__order));
}

template <typename _Tp>
static inline _Tp __c11_atomic_fetch_or(volatile _Atomic(_Tp)* __a,
_Tp __pattern, memory_order __order) {
return __atomic_fetch_or(&__a->__a_value, __pattern,
__gcc_atomic::__to_gcc_order(__order));
}

template <typename _Tp>
static inline _Tp __c11_atomic_fetch_or(_Atomic(_Tp)* __a, _Tp __pattern,
memory_order __order) {
return __atomic_fetch_or(&__a->__a_value, __pattern,
__gcc_atomic::__to_gcc_order(__order));
}

template <typename _Tp>
static inline _Tp __c11_atomic_fetch_xor(volatile _Atomic(_Tp)* __a,
_Tp __pattern, memory_order __order) {
return __atomic_fetch_xor(&__a->__a_value, __pattern,
__gcc_atomic::__to_gcc_order(__order));
}

template <typename _Tp>
static inline _Tp __c11_atomic_fetch_xor(_Atomic(_Tp)* __a, _Tp __pattern,
memory_order __order) {
return __atomic_fetch_xor(&__a->__a_value, __pattern,
__gcc_atomic::__to_gcc_order(__order));
}
#endif // _GNUC_VER >= 407

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_Tp
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