Use a CAS loop if atomic<Floating>::fetch_add() isn't available

1 files changed, 13 insertions, 1 deletions

diff --git a/zencore/stats.cpp b/zencore/stats.cpp
index 1bb6f6de0..595c45c3f 100644
--- a/zencore/stats.cpp
+++ b/zencore/stats.cpp
@@ -46,7 +46,19 @@ RawEWMA::Tick(double Alpha, uint64_t Interval, uint64_t Count, bool IsInitialUpd
 	}
 	else
 	{
-		m_Rate.fetch_add(Alpha * (InstantRate - m_Rate));
+		double Delta = Alpha * (InstantRate - m_Rate);
+
+#if defined(__cpp_lib_atomic_float)
+		m_Rate.fetch_add(Delta);
+#else
+		double Value = m_Rate.load(std::memory_order_acquire);
+		double Next;
+		do
+		{
+			Next = Value + Delta;
+		}
+		while (!m_Rate.compare_exchange_weak(Value, Next, std::memory_order_relaxed));
+#endif
 	}
 }