perf diff: Change formula methods to work with pair directly

Changing formula methods to operate over hist entry and its pair
directly. This makes the code more obvious and readable, instead of all
time checking for pair being != NULL.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1354110769-2998-7-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c
index 108e5ed..1785bab 100644
--- a/tools/perf/ui/hist.c
+++ b/tools/perf/ui/hist.c
@@ -389,10 +389,13 @@
 
 static int hpp__entry_formula(struct perf_hpp *hpp, struct hist_entry *he)
 {
+	struct hist_entry *pair = hist_entry__next_pair(he);
 	const char *fmt = symbol_conf.field_sep ? "%s" : "%-70s";
 	char buf[96] = " ";
 
-	perf_diff__formula(buf, sizeof(buf), he);
+	if (pair)
+		perf_diff__formula(he, pair, buf, sizeof(buf));
+
 	return scnprintf(hpp->buf, hpp->size, fmt, buf);
 }