[libc-commits] [libc] [libc][cpp] add `atomic_signal_fence` (PR #82138)

[via libc-commits]

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@@ -161,6 +161,21 @@ LIBC_INLINE void atomic_thread_fence(MemoryOrder mem_ord) {
 #endif
 }
 
+// Establishes memory synchronization ordering of non-atomic and relaxed atomic
+// accesses, as instructed by order, between a thread and a signal handler
+// executed on the same thread. This is equivalent to atomic_thread_fence,
+// except no instructions for memory ordering are issued. Only reordering of
+// the instructions by the compiler is suppressed as order instructs.
+LIBC_INLINE void atomic_signal_fence(MemoryOrder mem_ord) {
+#if __has_builtin(__atomic_signal_fence)
+  __atomic_signal_fence(int(mem_ord));
+#else
+  // if the builtin is not ready, use asm as a full compiler barrier.
+  (void)mem_ord;
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lntue wrote:

Do you mind removing C-style casting from this file?  Thanks,

https://github.com/llvm/llvm-project/pull/82138