perf stat: Only auto-merge events that are PMU aliases

Peter reported that when he explicitely asked for multiple events with
the same name on the command line it got coalesced into just one line,
i.e.:

# perf stat -e cycles -e cycles -e cycles usleep 1

Performance counter stats for 'usleep 1':

3,269,652 cycles

0.000884123 seconds time elapsed

#

And while there is the --no-merges option to disable that auto-merging,
this is a blunt change in behaviour for such explicit request, so change
the code so that this auto merging is done only when handling the multi
PMU aliases with the same name that introduced this coalescing,
restoring the previous behaviour for the explicit case:

# perf stat -e cycles -e cycles -e cycles usleep 1

Performance counter stats for 'usleep 1':

1,472,837 cycles
1,472,837 cycles
1,472,837 cycles

0.001764870 seconds time elapsed

#

Reported-by: Peter Zijlstra <[e-mail]>
Acked-by: Andi Kleen <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Wang Nan <[e-mail]>
Fixes: 430daf2dc7af ("perf stat: Collapse identically named events")
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-stat.c

···
 	if (counter->merged_stat)
 		return false;
 	cb(counter, data, true);
-	if (!no_merge)
+	if (!no_merge && counter->auto_merge_stats)
 		collect_all_aliases(counter, cb, data);
 	return true;
 }

tools/perf/util/evsel.h

···
 	bool			cmdline_group_boundary;
 	struct list_head	config_terms;
 	int			bpf_fd;
+	bool			auto_merge_stats;
 	bool			merged_stat;
 	const char *		metric_expr;
 	const char *		metric_name;

tools/perf/util/parse-events.c

···
 __add_event(struct list_head *list, int *idx,
 	    struct perf_event_attr *attr,
 	    char *name, struct cpu_map *cpus,
-	    struct list_head *config_terms)
+	    struct list_head *config_terms, bool auto_merge_stats)
 {
 	struct perf_evsel *evsel;
 
···
 	evsel->cpus        = cpu_map__get(cpus);
 	evsel->own_cpus    = cpu_map__get(cpus);
 	evsel->system_wide = !!cpus;
+	evsel->auto_merge_stats = auto_merge_stats;
 
 	if (name)
 		evsel->name = strdup(name);
···
 		     struct perf_event_attr *attr, char *name,
 		     struct list_head *config_terms)
 {
-	return __add_event(list, idx, attr, name, NULL, config_terms) ? 0 : -ENOMEM;
+	return __add_event(list, idx, attr, name, NULL, config_terms, false) ? 0 : -ENOMEM;
 }
 
 static int parse_aliases(char *str, const char *names[][PERF_EVSEL__MAX_ALIASES], int size)
···
 			 get_config_name(head_config), &config_terms);
 }
 
-int parse_events_add_pmu(struct parse_events_state *parse_state,
+static int __parse_events_add_pmu(struct parse_events_state *parse_state,
 			 struct list_head *list, char *name,
-			 struct list_head *head_config)
+			 struct list_head *head_config, bool auto_merge_stats)
 {
 	struct perf_event_attr attr;
 	struct perf_pmu_info info;
···
 
 	if (!head_config) {
 		attr.type = pmu->type;
-		evsel = __add_event(list, &parse_state->idx, &attr, NULL, pmu->cpus, NULL);
+		evsel = __add_event(list, &parse_state->idx, &attr, NULL, pmu->cpus, NULL, auto_merge_stats);
 		return evsel ? 0 : -ENOMEM;
 	}
 
···
 
 	evsel = __add_event(list, &parse_state->idx, &attr,
 			    get_config_name(head_config), pmu->cpus,
-			    &config_terms);
+			    &config_terms, auto_merge_stats);
 	if (evsel) {
 		evsel->unit = info.unit;
 		evsel->scale = info.scale;
···
 	}
 
 	return evsel ? 0 : -ENOMEM;
+}
+
+int parse_events_add_pmu(struct parse_events_state *parse_state,
+			 struct list_head *list, char *name,
+			 struct list_head *head_config)
+{
+	return __parse_events_add_pmu(parse_state, list, name, head_config, false);
 }
 
 int parse_events_multi_pmu_add(struct parse_events_state *parse_state,
···
 					return -1;
 				list_add_tail(&term->list, head);
 
-				if (!parse_events_add_pmu(parse_state, list,
-						  pmu->name, head)) {
+				if (!__parse_events_add_pmu(parse_state, list,
+							    pmu->name, head, true)) {
 					pr_debug("%s -> %s/%s/\n", str,
 						 pmu->name, alias->str);
 					ok++;