diff --git a/llvm/lib/Passes/StandardInstrumentations.cpp b/llvm/lib/Passes/StandardInstrumentations.cpp
--- a/llvm/lib/Passes/StandardInstrumentations.cpp
+++ b/llvm/lib/Passes/StandardInstrumentations.cpp
@@ -1553,8 +1553,6 @@
 protected:
   // Return the string surrounded by HTML to make it the appropriate colour.
   std::string colourize(std::string S, IRChangeDiffType T) const;
-  // Return the string containing the colour to use as a Dot attribute.
-  std::string attribute(IRChangeDiffType T) const;
 
   void createNode(StringRef Label, const BlockDataT<DCData> &BD,
                   IRChangeDiffType T) {
@@ -1646,10 +1644,6 @@
   return "<FONT COLOR=\"" + Colours[T] + "\">" + S + "</FONT>";
 }
 
-std::string DotCfgDiff::attribute(IRChangeDiffType T) const {
-  return "color=" + Colours[T];
-}
-
 std::string DotCfgDiffDisplayGraph::attribute(IRChangeDiffType T) const {
   return "color=" + Colours[T];
 }