perf tools: Allow sort dimensions to be registered more than once

So that the parent sort dimension can be registered twice: once
if we add it as an explicit sort dimension (-s parent) and twice
if we request a parent filter (-p foo).

We'll have only one parent sort dimension in the end but this
allows to override the default parent filter with we gave in "-p"
option. The goal of this is to prepare to allow the use of
"-s parent" and "-p foo" at the same time, ie: sort by filtered
parent.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Sam Liao <phyomh@gmail.com>

tools/perf/util/sort.c

@@ -260,15 +260,9 @@ int sort_dimension__add(const char *tok)
 	for (i = 0; i < ARRAY_SIZE(sort_dimensions); i++) {
 		struct sort_dimension *sd = &sort_dimensions[i];
 
-		if (sd->taken)
-			continue;
-
 		if (strncasecmp(tok, sd->name, strlen(tok)))
 			continue;
 
-		if (sd->entry->se_collapse)
-			sort__need_collapse = 1;
-
 		if (sd->entry == &sort_parent) {
 			int ret = regcomp(&parent_regex, parent_pattern, REG_EXTENDED);
 			if (ret) {
@@ -281,6 +275,12 @@ int sort_dimension__add(const char *tok)
 			sort__has_parent = 1;
 		}
 
+		if (sd->taken)
+			return 0;
+
+		if (sd->entry->se_collapse)
+			sort__need_collapse = 1;
+
 		if (list_empty(&hist_entry__sort_list)) {
 			if (!strcmp(sd->name, "pid"))
 				sort__first_dimension = SORT_PID;