libperf: Move perf's cpu_map__empty() to perf_cpu_map__empty()

So it's part of the libperf library as one of basic functions operating
on the perf_cpu_map class.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20190822111141.25823-4-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/lib/cpumap.c

@@ -237,3 +237,8 @@ int perf_cpu_map__nr(const struct perf_cpu_map *cpus)
 {
 	return cpus ? cpus->nr : 1;
 }
+
+bool perf_cpu_map__empty(const struct perf_cpu_map *map)
+{
+	return map ? map->map[0] == -1 : true;
+}

tools/perf/lib/include/perf/cpumap.h

@@ -4,6 +4,7 @@
 
 #include <perf/core.h>
 #include <stdio.h>
+#include <stdbool.h>
 
 struct perf_cpu_map;
 
@@ -14,6 +15,7 @@ LIBPERF_API struct perf_cpu_map *perf_cpu_map__get(struct perf_cpu_map *map);
 LIBPERF_API void perf_cpu_map__put(struct perf_cpu_map *map);
 LIBPERF_API int perf_cpu_map__cpu(const struct perf_cpu_map *cpus, int idx);
 LIBPERF_API int perf_cpu_map__nr(const struct perf_cpu_map *cpus);
+LIBPERF_API bool perf_cpu_map__empty(const struct perf_cpu_map *map);
 
 #define perf_cpu_map__for_each_cpu(cpu, idx, cpus)		\
 	for ((idx) = 0, (cpu) = perf_cpu_map__cpu(cpus, idx);	\

tools/perf/lib/libperf.map

@@ -8,6 +8,7 @@ LIBPERF_0.0.1 {
 		perf_cpu_map__read;
 		perf_cpu_map__nr;
 		perf_cpu_map__cpu;
+		perf_cpu_map__empty;
 		perf_thread_map__new_dummy;
 		perf_thread_map__set_pid;
 		perf_thread_map__comm;