diff --git a/llvm/lib/Support/CMakeLists.txt b/llvm/lib/Support/CMakeLists.txt
--- a/llvm/lib/Support/CMakeLists.txt
+++ b/llvm/lib/Support/CMakeLists.txt
@@ -26,7 +26,7 @@
       set(system_libs ${system_libs} ${TERMINFO_LIBS})
     endif()
   endif()
-  if( LLVM_ENABLE_THREADS AND HAVE_LIBATOMIC )
+  if( LLVM_ENABLE_THREADS AND (HAVE_LIBATOMIC OR HAVE_CXX_LIBATOMICS64) )
     set(system_libs ${system_libs} atomic)
   endif()
   set(system_libs ${system_libs} ${LLVM_PTHREAD_LIB})