Turns out there is a simpler way of getting a set difference in bash than parsing diff output.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172420 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/find-unused-diagnostics.sh b/utils/find-unused-diagnostics.sh
index cd6444d..c7fa01a 100755
--- a/utils/find-unused-diagnostics.sh
+++ b/utils/find-unused-diagnostics.sh
@@ -12,4 +12,4 @@
DIAGS_IN_SOURCES=$(grep -E --only-matching --no-filename '(err_|warn_|ext_|note_)[a-z_]+' $ALL_SOURCES)
# Print all diags that occur in the .td files but not in the source.
-diff -u <(sort -u <<< "$ALL_DIAGS") <(sort -u <<< "$DIAGS_IN_SOURCES") | sed -En 's/^-([a-z_]+)/\1/p'
+comm -23 <(sort -u <<< "$ALL_DIAGS") <(sort -u <<< "$DIAGS_IN_SOURCES")