trace: branch profiling should not print percent without data

Impact: cleanup on output of branch profiler

When a branch has not been taken, it does not make sense to show
a percentage incorrect or hit. This patch changes the behaviour
to print out a 'X' when the branch has not been executed yet.

For example:

 correct incorrect  %        Function                  File              Line
 ------- ---------  -        --------                  ----              ----
    2096        0   0 do_arch_prctl                  process_64.c         832
       0        0   X do_arch_prctl                  process_64.c         804
    2604        0   0 IS_ERR                         err.h                34
  130228     5765   4 __switch_to                    process_64.c         673
       0        0   X enable_TSC                     process_64.c         448
       0        0   X disable_TSC                    process_64.c         431
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace_branch.c

@@ -225,7 +225,7 @@ static int t_show(struct seq_file *m, void *v)
 {
 	struct ftrace_branch_data *p = v;
 	const char *f;
-	unsigned long percent;
+	long percent;
 
 	if (v == (void *)1) {
 		seq_printf(m, " correct incorrect  %% "
@@ -247,9 +247,13 @@ static int t_show(struct seq_file *m, void *v)
 		percent = p->incorrect * 100;
 		percent /= p->correct + p->incorrect;
 	} else
-		percent = p->incorrect ? 100 : 0;
+		percent = p->incorrect ? 100 : -1;
 
-	seq_printf(m, "%8lu %8lu %3lu ", p->correct, p->incorrect, percent);
+	seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
+	if (percent < 0)
+		seq_printf(m, "  X ");
+	else
+		seq_printf(m, "%3ld ", percent);
 	seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 	return 0;
 }