[PATCH] perf stat: Check aliases in should_skip_zero_counter

[Chun-Tse Shao <ctshao@google.com>]

Aggregation IDs (e.g. sockets, caches) with event zero counts are hidden
in aggregated modes (like `--per-socket`) because alias merging
aggregates counts but not CPU maps. This causes display logic to skip
aggregation IDs not present in the leader's map.

Instead of mutating CPU maps in `evsel__merge_aggr_counters` (which
could have side effects on shared CPU maps), check aliases in
`should_skip_zero_counter` to ensure all applicable aggregation IDs are
displayed.

Before the fix:
  $ perf stat -e amd_umc/config=0xff/ --per-socket -a -- sleep 1

   Performance counter stats for 'system wide':

  S0       12                  0      amd_umc/config=0xff/

         1.000721604 seconds time elapsed

After the fix:
  $ perf stat -e amd_umc/config=0xff/ --per-socket -a -- sleep 1

   Performance counter stats for 'system wide':

  S0       12                  0      amd_umc/config=0xff/
  S1       12                  0      amd_umc/config=0xff/

         1.000879376 seconds time elapsed

`perf test` looks good too.

Assisted-by: Gemini:gemini-3.1-pro-preview
Signed-off-by: Chun-Tse Shao <ctshao@google.com>
---
 tools/perf/util/stat-display.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
index 993f4c4b8f44..c12a3405118a 100644
--- a/tools/perf/util/stat-display.c
+++ b/tools/perf/util/stat-display.c
@@ -945,6 +945,27 @@ static bool should_skip_zero_counter(struct perf_stat_config *config,
 		if (aggr_cpu_id__equal(id, &own_id))
 			return false;
 	}
+
+	/*
+	 * If the counter is a leader in alias merging, check if the aggr id
+	 * matches any of its aliases.
+	 */
+	if (config->aggr_mode != AGGR_NONE && counter->first_wildcard_match == NULL) {
+		struct evsel *alias;
+
+		evlist__for_each_entry(counter->evlist, alias) {
+			if (alias->first_wildcard_match == counter) {
+				perf_cpu_map__for_each_cpu(cpu, idx, alias->core.cpus) {
+					struct aggr_cpu_id own_id =
+						config->aggr_get_id(config, cpu);
+
+					if (aggr_cpu_id__equal(id, &own_id))
+						return false;
+				}
+			}
+		}
+	}
+
 	return true;
 }
 
-- 
2.54.0.545.g6539524ca2-goog