perf test: Add basic 'perf diff' test

There are some old bug reports on perf diff crashing:

https://rhaas.blogspot.com/2012/06/perf-good-bad-ugly.html

Happening across them I was prompted to add two very basic tests that
will give some 'perf diff' coverage.
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20231120190408.281826-1-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/shell/diff.sh

+#!/bin/sh
+# perf diff tests
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+
+err=0
+perfdata1=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
+perfdata2=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
+perfdata3=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
+testprog="perf test -w thloop"
+testsym="test_loop"
+
+cleanup() {
+  rm -rf "${perfdata1}"
+  rm -rf "${perfdata1}".old
+  rm -rf "${perfdata2}"
+  rm -rf "${perfdata2}".old
+  rm -rf "${perfdata3}"
+  rm -rf "${perfdata3}".old
+
+  trap - EXIT TERM INT
+}
+
+trap_cleanup() {
+  cleanup
+  exit 1
+}
+trap trap_cleanup EXIT TERM INT
+
+make_data() {
+  file="$1"
+  if ! perf record -o "${file}" ${testprog} 2> /dev/null
+  then
+    echo "Workload record [Failed record]"
+    echo 1
+    return
+  fi
+  if ! perf report -i "${file}" -q | grep -q "${testsym}"
+  then
+    echo "Workload record [Failed missing output]"
+    echo 1
+    return
+  fi
+  echo 0
+}
+
+test_two_files() {
+  echo "Basic two file diff test"
+  err=$(make_data "${perfdata1}")
+  if [ $err != 0 ]
+  then
+    return
+  fi
+  err=$(make_data "${perfdata2}")
+  if [ $err != 0 ]
+  then
+    return
+  fi
+
+  if ! perf diff "${perfdata1}" "${perfdata2}" | grep -q "${testsym}"
+  then
+    echo "Basic two file diff test [Failed diff]"
+    err=1
+    return
+  fi
+  echo "Basic two file diff test [Success]"
+}
+
+test_three_files() {
+  echo "Basic three file diff test"
+  err=$(make_data "${perfdata1}")
+  if [ $err != 0 ]
+  then
+    return
+  fi
+  err=$(make_data "${perfdata2}")
+  if [ $err != 0 ]
+  then
+    return
+  fi
+  err=$(make_data "${perfdata3}")
+  if [ $err != 0 ]
+  then
+    return
+  fi
+
+  if ! perf diff "${perfdata1}" "${perfdata2}" "${perfdata3}" | grep -q "${testsym}"
+  then
+    echo "Basic three file diff test [Failed diff]"
+    err=1
+    return
+  fi
+  echo "Basic three file diff test [Success]"
+}
+
+test_two_files
+test_three_files
+
+cleanup
+exit $err