perf trace: Cache the is_exit syscall test

No need to use two strcmp calls per syscall entry, do it just once, when
reading the per syscall info.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-lymtxhz0mg3adyt5e2pssn8f@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-trace.c

@@ -1108,6 +1108,7 @@ struct syscall {
 	struct event_format *tp_format;
 	const char	    *name;
 	bool		    filtered;
+	bool		    is_exit;
 	struct syscall_fmt  *fmt;
 	size_t		    (**arg_scnprintf)(char *bf, size_t size, struct syscall_arg *arg);
 	void		    **arg_parm;
@@ -1473,6 +1474,8 @@ static int trace__read_syscall_info(struct trace *trace, int id)
 	if (sc->tp_format == NULL)
 		return -1;
 
+	sc->is_exit = !strcmp(name, "exit_group") || !strcmp(name, "exit");
+
 	return syscall__set_arg_fmts(sc);
 }
 
@@ -1643,7 +1646,7 @@ static int trace__sys_enter(struct trace *trace, struct perf_evsel *evsel,
 	printed += syscall__scnprintf_args(sc, msg + printed, 1024 - printed,
 					   args, trace, thread);
 
-	if (!strcmp(sc->name, "exit_group") || !strcmp(sc->name, "exit")) {
+	if (sc->is_exit) {
 		if (!trace->duration_filter && !trace->summary_only) {
 			trace__fprintf_entry_head(trace, thread, 1, sample->time, trace->output);
 			fprintf(trace->output, "%-70s\n", ttrace->entry_str);