libperf cpumap: Add "any CPU"/dummy test function

It is common in the code currently to test a map for "empty" when in
fact the "any CPU"/dummy value of -1 is being sought. Add a new
function to enable this and document the behavior of two other
functions.

The term "any CPU" comes from perf_event_open, where the value is
consumed, but it is more typical in the code to see this value/map
referred to as the dummy value. This could be misleading due to the
dummy event and also dummy not being intention revealing, so it is hoped
to migrate the code to referring to this as "any CPU".
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ali Saidi <alisaidi@amazon.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Dmitrii Dolgov <9erthalion6@gmail.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kang Minchul <tegongkang@gmail.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Ming Wang <wangming01@loongson.cn>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20230527072210.2900565-4-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/perf/cpumap.c

@@ -356,6 +356,11 @@ bool perf_cpu_map__equal(const struct perf_cpu_map *lhs, const struct perf_cpu_m
 	return true;
 }
 
+bool perf_cpu_map__has_any_cpu(const struct perf_cpu_map *map)
+{
+	return map && __perf_cpu_map__cpu(map, 0).cpu == -1;
+}
+
 struct perf_cpu perf_cpu_map__max(const struct perf_cpu_map *map)
 {
 	struct perf_cpu result = {

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

@@ -18,6 +18,9 @@ struct perf_cache {
 
 struct perf_cpu_map;
 
+/**
+ * perf_cpu_map__dummy_new - a map with a singular "any CPU"/dummy -1 value.
+ */
 LIBPERF_API struct perf_cpu_map *perf_cpu_map__dummy_new(void);
 LIBPERF_API struct perf_cpu_map *perf_cpu_map__default_new(void);
 LIBPERF_API struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list);
@@ -30,11 +33,18 @@ LIBPERF_API struct perf_cpu_map *perf_cpu_map__intersect(struct perf_cpu_map *or
 LIBPERF_API void perf_cpu_map__put(struct perf_cpu_map *map);
 LIBPERF_API struct perf_cpu 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);
+/**
+ * perf_cpu_map__empty - is map either empty or the "any CPU"/dummy value.
+ */
 LIBPERF_API bool perf_cpu_map__empty(const struct perf_cpu_map *map);
 LIBPERF_API struct perf_cpu perf_cpu_map__max(const struct perf_cpu_map *map);
 LIBPERF_API bool perf_cpu_map__has(const struct perf_cpu_map *map, struct perf_cpu cpu);
 LIBPERF_API bool perf_cpu_map__equal(const struct perf_cpu_map *lhs,
 				     const struct perf_cpu_map *rhs);
+/**
+ * perf_cpu_map__any_cpu - Does the map contain the "any CPU"/dummy -1 value?
+ */
+LIBPERF_API bool perf_cpu_map__has_any_cpu(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);	\