1 files changed, 29 insertions, 0 deletions
diff --git a/cmake/modules/CheckAtomic.cmake b/cmake/modules/CheckAtomic.cmake
new file mode 100644
index 00000000000..0d63a82b97a
--- /dev/null
+++ b/cmake/modules/CheckAtomic.cmake
@@ -0,0 +1,29 @@
+# atomic builtins are required for threading support.
+
+INCLUDE(CheckCXXSourceCompiles)
+
+CHECK_CXX_SOURCE_COMPILES("
+#ifdef _MSC_VER
+#include <windows.h>
+#endif
+int main() {
+#ifdef _MSC_VER
+        volatile LONG val = 1;
+        MemoryBarrier();
+        InterlockedCompareExchange(&val, 0, 1);
+        InterlockedIncrement(&val);
+        InterlockedDecrement(&val);
+#else
+        volatile unsigned long val = 1;
+        __sync_synchronize();
+        __sync_val_compare_and_swap(&val, 1, 0);
+        __sync_add_and_fetch(&val, 1);
+        __sync_sub_and_fetch(&val, 1);
+#endif
+        return 0;
+      }
+" LLVM_HAS_ATOMICS)
+
+if( NOT LLVM_HAS_ATOMICS )
+  message(STATUS "Warning: LLVM will be built thread-unsafe because atomic builtins are missing")
+endif()