diff --git a/utils/find-unused-diagnostics.sh b/utils/find-unused-diagnostics.sh
new file mode 100644
index 0000000..89b7f7a
--- /dev/null
+++ b/utils/find-unused-diagnostics.sh
@@ -0,0 +1,19 @@
+#!/bin/bash
+#
+# This script produces a list of all diagnostics that are defined
+# in Diagnostic*.td files but not used in sources.
+#
+
+ALL_DIAGS=$(mktemp)
+ALL_SOURCES=$(mktemp)
+
+grep -E --only-matching --no-filename '(err_|warn_|ext_|note_)[a-z_]+ ' ./include/clang/Basic/Diagnostic*.td > $ALL_DIAGS
+find lib include tools -name \*.cpp -or -name \*.h > $ALL_SOURCES
+for DIAG in $(cat $ALL_DIAGS); do
+  if ! grep -r $DIAG $(cat $ALL_SOURCES) > /dev/null; then
+    echo $DIAG
+  fi;
+done
+
+rm $ALL_DIAGS $ALL_SOURCES
+