Fix a comment typo.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120235 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index fe7c41c..994dbd4 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3438,7 +3438,7 @@
     }
     if (BothLiveOut)
       // Both unextended and extended values are live out. There had better be
-      // good a reason for the transformation.
+      // a good reason for the transformation.
       return ExtendNodes.size();
   }
   return true;