microoptimize this hot method, also making it more 
consistent with other similar ones.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99997 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/DebugInfo.cpp b/lib/Analysis/DebugInfo.cpp
index fda69ac..f12552d 100644
--- a/lib/Analysis/DebugInfo.cpp
+++ b/lib/Analysis/DebugInfo.cpp
@@ -96,9 +96,8 @@
   if (DbgNode == 0)
     return DIDescriptor();
 
-  if (Elt < DbgNode->getNumOperands() && DbgNode->getOperand(Elt))
-    return DIDescriptor(dyn_cast<MDNode>(DbgNode->getOperand(Elt)));
-
+  if (Elt < DbgNode->getNumOperands())
+    return DIDescriptor(dyn_cast_or_null<MDNode>(DbgNode->getOperand(Elt)));
   return DIDescriptor();
 }