Add cast to appease windows builder. Fixes build break introduced in r280306.

llvm-svn: 280311
diff --git a/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp b/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
index 375be2a..93a29fd 100644
--- a/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
@@ -428,7 +428,7 @@
       bool ThreeElement = N->getNumOperands() == 3;
       if (!ThreeElement && N->getNumOperands() != 2)
         continue;
-      if (N->getOperand(ThreeElement ? 2 : 1) != CU)
+      if (dyn_cast<MDNode>(N->getOperand(ThreeElement ? 2 : 1)) != CU)
         continue;
 
       if (ThreeElement) {