[RFC][PATCH 08/12] tracing/filter: Optimize short ciruit check

[Steven Rostedt <rostedt@goodmis.org>]

[-- Attachment #1: 0008-tracing-filter-Optimize-short-ciruit-check.patch --]
[-- Type: text/plain, Size: 1406 bytes --]

From: Steven Rostedt <srostedt@redhat.com>

The test if we should break out early for OR and AND operations
can be optimized by comparing the current result with
  (pred->op == OP_OR)

That is if the result is true and the op is an OP_OR, or
if the result is false and the op is not an OP_OR (thus an OP_AND)
we can break out early in either case. Otherwise we continue
processing.

Cc: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_events_filter.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 2677924..afe59ab 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -426,9 +426,15 @@ int filter_match_preds(struct event_filter *filter, void *rec)
 					       pred->parent, &move);
 			continue;
 		case MOVE_UP_FROM_LEFT:
-			/* Check for short circuits */
-			if ((match && pred->op == OP_OR) ||
-			    (!match && pred->op == OP_AND)) {
+			/*
+			 * Check for short circuits.
+			 *
+			 * Optimization: !!match == (pred->op == OP_OR)
+			 *   is the same as:
+			 * if ((match && pred->op == OP_OR) ||
+			 *     (!match && pred->op == OP_AND))
+			 */
+			if (!!match == (pred->op == OP_OR))
 				if (pred == root)
 					break;
 				pred = get_pred_parent(pred, preds,
-- 
1.7.2.3