Implement is_always_lock_free
Summary:
This was voted into C++17 at the Jacksonville meeting. The final P0152R1
paper will be in the upcoming post-Jacksonville mailing, and is also
available here:
http://jfbastien.github.io/papers/P0152R1.html
Reviewers: mclow.lists, rsmith
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D17951
llvm-svn: 264413
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: b95ee819f2fdb60463f8317e57134c0f27c4ccb3
diff --git a/include/atomic b/include/atomic
index abec2a0..dc117e9 100644
--- a/include/atomic
+++ b/include/atomic
@@ -17,6 +17,10 @@
namespace std
{
+// feature test macro
+
+#define __cpp_lib_atomic_is_always_lock_free // as specified by SG10
+
// order and consistency
typedef enum memory_order
@@ -89,6 +93,7 @@
template <class T>
struct atomic
{
+ static constexpr bool is_always_lock_free;
bool is_lock_free() const volatile noexcept;
bool is_lock_free() const noexcept;
void store(T desr, memory_order m = memory_order_seq_cst) volatile noexcept;
@@ -127,6 +132,7 @@
template <>
struct atomic<integral>
{
+ static constexpr bool is_always_lock_free;
bool is_lock_free() const volatile noexcept;
bool is_lock_free() const noexcept;
void store(integral desr, memory_order m = memory_order_seq_cst) volatile noexcept;
@@ -202,6 +208,7 @@
template <class T>
struct atomic<T*>
{
+ static constexpr bool is_always_lock_free;
bool is_lock_free() const volatile noexcept;
bool is_lock_free() const noexcept;
void store(T* desr, memory_order m = memory_order_seq_cst) volatile noexcept;
@@ -540,6 +547,11 @@
#error <atomic> is not implemented
#endif
+#if _LIBCPP_STD_VER > 14
+// FIXME: use the right feature test macro value as chose by SG10.
+# define __cpp_lib_atomic_is_always_lock_free 201603L
+#endif
+
_LIBCPP_BEGIN_NAMESPACE_STD
typedef enum memory_order
@@ -825,6 +837,17 @@
return __y;
}
+#define ATOMIC_BOOL_LOCK_FREE __GCC_ATOMIC_BOOL_LOCK_FREE
+#define ATOMIC_CHAR_LOCK_FREE __GCC_ATOMIC_CHAR_LOCK_FREE
+#define ATOMIC_CHAR16_T_LOCK_FREE __GCC_ATOMIC_CHAR16_T_LOCK_FREE
+#define ATOMIC_CHAR32_T_LOCK_FREE __GCC_ATOMIC_CHAR32_T_LOCK_FREE
+#define ATOMIC_WCHAR_T_LOCK_FREE __GCC_ATOMIC_WCHAR_T_LOCK_FREE
+#define ATOMIC_SHORT_LOCK_FREE __GCC_ATOMIC_SHORT_LOCK_FREE
+#define ATOMIC_INT_LOCK_FREE __GCC_ATOMIC_INT_LOCK_FREE
+#define ATOMIC_LONG_LOCK_FREE __GCC_ATOMIC_LONG_LOCK_FREE
+#define ATOMIC_LLONG_LOCK_FREE __GCC_ATOMIC_LLONG_LOCK_FREE
+#define ATOMIC_POINTER_LOCK_FREE __GCC_ATOMIC_POINTER_LOCK_FREE
+
// general atomic<T>
template <class _Tp, bool = is_integral<_Tp>::value && !is_same<_Tp, bool>::value>
@@ -832,6 +855,10 @@
{
mutable _Atomic(_Tp) __a_;
+#if defined(__cpp_lib_atomic_is_always_lock_free)
+ static _LIBCPP_CONSTEXPR bool is_always_lock_free = __atomic_always_lock_free(sizeof(__a_), 0);
+#endif
+
_LIBCPP_INLINE_VISIBILITY
bool is_lock_free() const volatile _NOEXCEPT
{
@@ -920,6 +947,11 @@
#endif // _LIBCPP_HAS_NO_DELETED_FUNCTIONS
};
+#if defined(__cpp_lib_atomic_is_always_lock_free)
+template <class _Tp, bool __b>
+_LIBCPP_CONSTEXPR bool __atomic_base<_Tp, __b>::is_always_lock_free;
+#endif
+
// atomic<Integral>
template <class _Tp>
@@ -1789,17 +1821,6 @@
#define ATOMIC_FLAG_INIT {false}
#define ATOMIC_VAR_INIT(__v) {__v}
-#define ATOMIC_BOOL_LOCK_FREE __GCC_ATOMIC_BOOL_LOCK_FREE
-#define ATOMIC_CHAR_LOCK_FREE __GCC_ATOMIC_CHAR_LOCK_FREE
-#define ATOMIC_CHAR16_T_LOCK_FREE __GCC_ATOMIC_CHAR16_T_LOCK_FREE
-#define ATOMIC_CHAR32_T_LOCK_FREE __GCC_ATOMIC_CHAR32_T_LOCK_FREE
-#define ATOMIC_WCHAR_T_LOCK_FREE __GCC_ATOMIC_WCHAR_T_LOCK_FREE
-#define ATOMIC_SHORT_LOCK_FREE __GCC_ATOMIC_SHORT_LOCK_FREE
-#define ATOMIC_INT_LOCK_FREE __GCC_ATOMIC_INT_LOCK_FREE
-#define ATOMIC_LONG_LOCK_FREE __GCC_ATOMIC_LONG_LOCK_FREE
-#define ATOMIC_LLONG_LOCK_FREE __GCC_ATOMIC_LLONG_LOCK_FREE
-#define ATOMIC_POINTER_LOCK_FREE __GCC_ATOMIC_POINTER_LOCK_FREE
-
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP_ATOMIC