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 <mark.rutland@arm.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1468577293-19667-3-git-send-email-mark.rutland@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/cpumap.c

@@ -588,15 +588,25 @@ int cpu__setup_cpunode_map(void)
 }
 
 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

@@ -68,5 +68,7 @@ int cpu_map__build_map(struct cpu_map *cpus, struct cpu_map **res,
 		       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 */