perf evsel: Provide way to extract integer value from format_field

Out of perf_evsel__intval(), that requires passing the variable name,
that will then be searched in the list of tracepoint variables for the
given evsel.

In cases such as syscall file descriptor ("fd") tracking, this is
wasteful, we need just to use perf_evsel__field() and cache the
format_field.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-r6f89jx9j5nkx037d0naviqy@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel.c

@@ -2251,17 +2251,11 @@ void *perf_evsel__rawptr(struct perf_evsel *evsel, struct perf_sample *sample,
 	return sample->raw_data + offset;
 }
 
-u64 perf_evsel__intval(struct perf_evsel *evsel, struct perf_sample *sample,
-		       const char *name)
+u64 format_field__intval(struct format_field *field, struct perf_sample *sample,
+			 bool needs_swap)
 {
-	struct format_field *field = perf_evsel__field(evsel, name);
-	void *ptr;
 	u64 value;
-
-	if (!field)
-		return 0;
-
-	ptr = sample->raw_data + field->offset;
+	void *ptr = sample->raw_data + field->offset;
 
 	switch (field->size) {
 	case 1:
@@ -2279,7 +2273,7 @@ u64 perf_evsel__intval(struct perf_evsel *evsel, struct perf_sample *sample,
 		return 0;
 	}
 
-	if (!evsel->needs_swap)
+	if (!needs_swap)
 		return value;
 
 	switch (field->size) {
@@ -2296,6 +2290,17 @@ u64 perf_evsel__intval(struct perf_evsel *evsel, struct perf_sample *sample,
 	return 0;
 }
 
+u64 perf_evsel__intval(struct perf_evsel *evsel, struct perf_sample *sample,
+		       const char *name)
+{
+	struct format_field *field = perf_evsel__field(evsel, name);
+
+	if (!field)
+		return 0;
+
+	return field ? format_field__intval(field, sample, evsel->needs_swap) : 0;
+}
+
 bool perf_evsel__fallback(struct perf_evsel *evsel, int err,
 			  char *msg, size_t msgsize)
 {

tools/perf/util/evsel.h

@@ -261,6 +261,8 @@ static inline char *perf_evsel__strval(struct perf_evsel *evsel,
 
 struct format_field;
 
+u64 format_field__intval(struct format_field *field, struct perf_sample *sample, bool needs_swap);
+
 struct format_field *perf_evsel__field(struct perf_evsel *evsel, const char *name);
 
 #define perf_evsel__match(evsel, t, c)		\