correctly check for visited md

Author: jchlanda

llvm/lib/SYCLLowerIR/LocalAccessorToSharedMemory.cpp

@@ -253,10 +253,11 @@ class LocalAccessorToSharedMemory : public ModulePass {
     // the same metadata, recognise visited ones.
     SmallSet<MDNode *, 4> Visited;
     for (auto *MetadataNode : NvvmMetadata->operands()) {
-      Visited.insert(MetadataNode);
       if (Visited.contains(MetadataNode) || MetadataNode->getNumOperands() != 3)
         continue;
 
+      Visited.insert(MetadataNode);
+
       // NVPTX identifies kernel entry points using metadata nodes of the form:
       //   !X = !{<function>, !"kernel", i32 1}
       const MDOperand &TypeOperand = MetadataNode->getOperand(1);