perf tools: Uniquify the event name if there's no other matched event

Currently by default we try to match the user specified PMU name to all PMU units available and use them to aggregate all matched PMUs event counts into one 'pattern' event.

While this is useful for uncore events, it screws up names for other events, where this is not desirable, like:

Before:

  # perf stat -e cp/cpu-cycles/ kill

Performance counter stats for 'kill':

           1,573,757      cp/cpu-cycles/

Keeping the pattern matching logic, but making the name unique in case there's no other match found. That fixes the example above and hopefully does not screw up anything else.

After:

  # perf stat -e cp/cpu-cycles/ kill

Performance counter stats for 'kill':

           1,573,757      cpu/cpu-cycles/

---
 tools/perf/builtin-stat.c | 9 +++++++++
 1 file changed, 9 insertions(+)

index 4d24c32e6c38..b32cd8bda0b5 100644
@@ -1354,6 +1354,7 @@ static void collect_all_aliases(struct perf_evsel *counter,
 			    void *data)
 {
 	struct perf_evsel *alias;
+	int cnt = 0;
 
 	alias = list_prepare_entry(counter, &(evsel_list->entries), node);
 	list_for_each_entry_continue (alias, &evsel_list->entries, node) {

@@ -1365,7 +1366,15 @@ static void collect_all_aliases(struct perf_evsel *counter,
 			break;
 		alias->merged_stat = true;
 		cb(alias, data, false);
+		cnt++;
 	}
+
+	/*
+	 * There's no matching event to aggregate
+	 * counts with, fix the event name
+	 */
+	if (!cnt)
+		uniquify_event_name(counter);
 }
 
 static bool collect_data(struct perf_evsel *counter,

2.13.6