Collapse logic and move and reword comment for clarity.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187013 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/IR/DebugInfo.cpp b/lib/IR/DebugInfo.cpp
index c42a9a3..c78b8c2 100644
--- a/lib/IR/DebugInfo.cpp
+++ b/lib/IR/DebugInfo.cpp
@@ -417,10 +417,12 @@
 bool DICompileUnit::Verify() const {
   if (!isCompileUnit())
     return false;
-  StringRef N = getFilename();
-  if (N.empty())
+
+  // Don't bother verifying the compilation directory or producer string
+  // as those could be empty.
+  if (getFilename().empty())
     return false;
-  // It is possible that directory and produce string is empty.
+
   return DbgNode->getNumOperands() == 13;
 }