tracing/filter: Optimize short ciruit check

Steven Rostedt · rostedt · commit 55719274188f · 2011-02-07T20:56:19.000-05:00
The test if we should break out early for OR and AND operations
can be optimized by comparing the current result with
  (pred-&gt;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 &lt;tzanussi@gmail.com&gt;
Signed-off-by: Steven Rostedt &lt;rostedt@goodmis.org&gt;
diff --git 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,
