[libcxx] r264413 - Implement is_always_lock_free

JF Bastien via cfe-commits cfe-commits at lists.llvm.org
Fri Mar 25 08:48:21 PDT 2016


Author: jfb
Date: Fri Mar 25 10:48:21 2016
New Revision: 264413

URL: http://llvm.org/viewvc/llvm-project?rev=264413&view=rev
Log:
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

Added:
    libcxx/trunk/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp
Modified:
    libcxx/trunk/include/atomic

Modified: libcxx/trunk/include/atomic
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/atomic?rev=264413&r1=264412&r2=264413&view=diff
==============================================================================
--- libcxx/trunk/include/atomic (original)
+++ libcxx/trunk/include/atomic Fri Mar 25 10:48:21 2016
@@ -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 @@ void
 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 @@ struct atomic
 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 @@ struct atomic<integral>
 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 @@ void atomic_signal_fence(memory_order m)
 #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 @@ kill_dependency(_Tp __y) _NOEXCEPT
     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 @@ struct __atomic_base  // false
 {
     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 @@ private:
 #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 @@ typedef atomic<uintmax_t> atomic_uintmax
 #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

Added: libcxx/trunk/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp?rev=264413&view=auto
==============================================================================
--- libcxx/trunk/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp (added)
+++ libcxx/trunk/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp Fri Mar 25 10:48:21 2016
@@ -0,0 +1,101 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: libcpp-has-no-threads, c++98, c++03, c++11, c++14
+
+// <atomic>
+
+// static constexpr bool is_always_lock_free;
+
+#include <atomic>
+#include <cassert>
+
+#if !defined(__cpp_lib_atomic_is_always_lock_free)
+# error Feature test macro missing.
+#endif
+
+template <typename T> void checkAlwaysLockFree() {
+  if (std::atomic<T>::is_always_lock_free)
+    assert(std::atomic<T>().is_lock_free());
+}
+
+int main()
+{
+// structs and unions can't be defined in the template invocation.
+// Work around this with a typedef.
+#define CHECK_ALWAYS_LOCK_FREE(T)                                              \
+  do {                                                                         \
+    typedef T type;                                                            \
+    checkAlwaysLockFree<type>();                                               \
+  } while (0)
+
+    CHECK_ALWAYS_LOCK_FREE(bool);
+    CHECK_ALWAYS_LOCK_FREE(char);
+    CHECK_ALWAYS_LOCK_FREE(signed char);
+    CHECK_ALWAYS_LOCK_FREE(unsigned char);
+    CHECK_ALWAYS_LOCK_FREE(char16_t);
+    CHECK_ALWAYS_LOCK_FREE(char32_t);
+    CHECK_ALWAYS_LOCK_FREE(wchar_t);
+    CHECK_ALWAYS_LOCK_FREE(short);
+    CHECK_ALWAYS_LOCK_FREE(unsigned short);
+    CHECK_ALWAYS_LOCK_FREE(int);
+    CHECK_ALWAYS_LOCK_FREE(unsigned int);
+    CHECK_ALWAYS_LOCK_FREE(long);
+    CHECK_ALWAYS_LOCK_FREE(unsigned long);
+    CHECK_ALWAYS_LOCK_FREE(long long);
+    CHECK_ALWAYS_LOCK_FREE(unsigned long long);
+    CHECK_ALWAYS_LOCK_FREE(std::nullptr_t);
+    CHECK_ALWAYS_LOCK_FREE(void*);
+    CHECK_ALWAYS_LOCK_FREE(float);
+    CHECK_ALWAYS_LOCK_FREE(double);
+    CHECK_ALWAYS_LOCK_FREE(long double);
+    CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(1 * sizeof(int)))));
+    CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(2 * sizeof(int)))));
+    CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(4 * sizeof(int)))));
+    CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(16 * sizeof(int)))));
+    CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(32 * sizeof(int)))));
+    CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(1 * sizeof(float)))));
+    CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(2 * sizeof(float)))));
+    CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(4 * sizeof(float)))));
+    CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(16 * sizeof(float)))));
+    CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(32 * sizeof(float)))));
+    CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(1 * sizeof(double)))));
+    CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(2 * sizeof(double)))));
+    CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(4 * sizeof(double)))));
+    CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(16 * sizeof(double)))));
+    CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(32 * sizeof(double)))));
+    CHECK_ALWAYS_LOCK_FREE(struct{});
+    CHECK_ALWAYS_LOCK_FREE(struct{ int i; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ int i[2]; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ long long int i[2]; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ long long int i[4]; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ long long int i[8]; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ long long int i[16]; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ char c; /* padding */ long long int i; });
+    CHECK_ALWAYS_LOCK_FREE(union{ int i; float f; });
+
+    // C macro and static constexpr must be consistent.
+    static_assert(std::atomic<bool>::is_always_lock_free == (2 == ATOMIC_BOOL_LOCK_FREE));
+    static_assert(std::atomic<char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE));
+    static_assert(std::atomic<signed char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE));
+    static_assert(std::atomic<unsigned char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE));
+    static_assert(std::atomic<char16_t>::is_always_lock_free == (2 == ATOMIC_CHAR16_T_LOCK_FREE));
+    static_assert(std::atomic<char32_t>::is_always_lock_free == (2 == ATOMIC_CHAR32_T_LOCK_FREE));
+    static_assert(std::atomic<wchar_t>::is_always_lock_free == (2 == ATOMIC_WCHAR_T_LOCK_FREE));
+    static_assert(std::atomic<short>::is_always_lock_free == (2 == ATOMIC_SHORT_LOCK_FREE));
+    static_assert(std::atomic<unsigned short>::is_always_lock_free == (2 == ATOMIC_SHORT_LOCK_FREE));
+    static_assert(std::atomic<int>::is_always_lock_free == (2 == ATOMIC_INT_LOCK_FREE));
+    static_assert(std::atomic<unsigned int>::is_always_lock_free == (2 == ATOMIC_INT_LOCK_FREE));
+    static_assert(std::atomic<long>::is_always_lock_free == (2 == ATOMIC_LONG_LOCK_FREE));
+    static_assert(std::atomic<unsigned long>::is_always_lock_free == (2 == ATOMIC_LONG_LOCK_FREE));
+    static_assert(std::atomic<long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE));
+    static_assert(std::atomic<unsigned long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE));
+    static_assert(std::atomic<void*>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE));
+    static_assert(std::atomic<std::nullptr_t>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE));
+}




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