[PATCH] perf stat: Merge CPU maps when merging uncore aliases

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

Sockets with event zero counts are hidden in `perf stat --per-socket`
because alias merging aggregates counts but not CPU maps. This causes
the display logic to incorrectly skip sockets not present in the leader
instance's map.

For example, with AMD_UMC:
  $ cat /sys/bus/event_source/devices/amd_umc*/cpumask
  0
  ...
  128
  ...

  $ 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/

         1.000777829 seconds time elapsed

Merge CPU maps in `evsel__merge_aggr_counters` to ensure the aggregated
event correctly reflects all underlying PMU instances.

After 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/

         1.000666681 seconds time elapsed

Signed-off-by: Chun-Tse Shao <ctshao@google.com>
---
 tools/perf/util/stat.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
index 14d169e22e8f..d696d217f98d 100644
--- a/tools/perf/util/stat.c
+++ b/tools/perf/util/stat.c
@@ -535,6 +535,12 @@ static int evsel__merge_aggr_counters(struct evsel *evsel, struct evsel *alias)
 		aggr_counts_a->run += aggr_counts_b->run;
 	}
 
+	/*
+	 * Merge the CPU maps so that the display logic (e.g. should_skip_zero_counter)
+	 * knows this merged event covers all CPUs from both aliases.
+	 */
+	perf_cpu_map__merge(&evsel->core.cpus, alias->core.cpus);
+
 	return 0;
 }
 
-- 
2.54.0.rc1.555.g9c883467ad-goog