Index: include/llvm/Support/ThreadPool.h
===================================================================
--- include/llvm/Support/ThreadPool.h
+++ include/llvm/Support/ThreadPool.h
@@ -33,6 +33,7 @@
 #pragma warning(pop)
 #endif
 
+#include <atomic>
 #include <condition_variable>
 #include <functional>
 #include <memory>