perf stat: Refactor __run_perf_stat() common code

This extracts common code from the branches of the forks if-then-else.

enable_counters(), which was at the beginning of both branches of the
conditional, is now unconditional; evlist__start_workload() is extracted
to a different if, which enables making the common clocking code
unconditional.
Reviewed-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Adrián Herrera Arcila <adrian.herrera@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.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>
Cc: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/r/20220729161244.10522-1-adrian.herrera@arm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-stat.c

@@ -967,18 +967,18 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
 			return err;
 	}
 
-	/*
-	 * Enable counters and exec the command:
-	 */
-	if (forks) {
-		err = enable_counters();
-		if (err)
-			return -1;
+	err = enable_counters();
+	if (err)
+		return -1;
+
+	/* Exec the command, if any */
+	if (forks)
 		evlist__start_workload(evsel_list);
 
-		t0 = rdclock();
-		clock_gettime(CLOCK_MONOTONIC, &ref_time);
+	t0 = rdclock();
+	clock_gettime(CLOCK_MONOTONIC, &ref_time);
 
+	if (forks) {
 		if (interval || timeout || evlist__ctlfd_initialized(evsel_list))
 			status = dispatch_events(forks, timeout, interval, &times);
 		if (child_pid != -1) {
@@ -996,13 +996,6 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
 		if (WIFSIGNALED(status))
 			psignal(WTERMSIG(status), argv[0]);
 	} else {
-		err = enable_counters();
-		if (err)
-			return -1;
-
-		t0 = rdclock();
-		clock_gettime(CLOCK_MONOTONIC, &ref_time);
-
 		status = dispatch_events(forks, timeout, interval, &times);
 	}