Reduce dyn_cast<> to isa<> or cast<> where possible.

No functional change intended.

llvm-svn: 234586
diff --git a/llvm/utils/yaml-bench/YAMLBench.cpp b/llvm/utils/yaml-bench/YAMLBench.cpp
index 8bd1ea1..872f586 100644
--- a/llvm/utils/yaml-bench/YAMLBench.cpp
+++ b/llvm/utils/yaml-bench/YAMLBench.cpp
@@ -117,7 +117,7 @@
     outs() << indent(Indent) << "}";
   } else if (yaml::AliasNode *an = dyn_cast<yaml::AliasNode>(n)){
     outs() << "*" << an->getName();
-  } else if (dyn_cast<yaml::NullNode>(n)) {
+  } else if (isa<yaml::NullNode>(n)) {
     outs() << prettyTag(n) << " null";
   }
 }