perf cpu_map: Add more helpers

In some cases it's necessry to figure out the map-local index of a given
Linux logical CPU ID. Add a new helper, cpu_map__idx, to acquire this.
As the logic is largely the same as the existing cpu_map__has, this is
rewritten in terms of the new helper.

At the same time, add the inverse operation, cpu_map__cpu, which yields
the logical CPU id for a map-local index. While this can be performed
manually, wrapping this in a helper can make code more legible.

Signed-off-by: Mark Rutland <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: He Kuang <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/cpumap.c

···
 
 bool cpu_map__has(struct cpu_map *cpus, int cpu)
 {
+	return cpu_map__idx(cpus, cpu) != -1;
+}
+
+int cpu_map__idx(struct cpu_map *cpus, int cpu)
+{
 	int i;
 
 	for (i = 0; i < cpus->nr; ++i) {
 		if (cpus->map[i] == cpu)
-			return true;
+			return i;
 	}
 
-	return false;
+	return -1;
+}
+
+int cpu_map__cpu(struct cpu_map *cpus, int idx)
+{
+	return cpus->map[idx];
 }
 
 size_t cpu_map__snprint(struct cpu_map *map, char *buf, size_t size)

tools/perf/util/cpumap.h

···
 		       int (*f)(struct cpu_map *map, int cpu, void *data),
 		       void *data);
 
+int cpu_map__cpu(struct cpu_map *cpus, int idx);
 bool cpu_map__has(struct cpu_map *cpus, int cpu);
+int cpu_map__idx(struct cpu_map *cpus, int cpu);
 #endif /* __PERF_CPUMAP_H */