Prefer const references for Pin/Channel maps

Another micro-optmization shaving off some ten microseconds for every
plugin. Also copying maps isn't RT-safe.

This may however cause issue if const map references can change
while a plugin is running.

1 files changed, 11 insertions, 12 deletions

diff --git a/libs/ardour/plugin_insert.cc b/libs/ardour/plugin_insert.cc
index 23c9f8eb7a..b24d065b5b 100644
--- a/libs/ardour/plugin_insert.cc
+++ b/libs/ardour/plugin_insert.cc
@@ -824,14 +824,14 @@ PluginInsert::inplace_silence_unconnected (BufferSet& bufs, const PinMappings& o
 void
 PluginInsert::connect_and_run (BufferSet& bufs, samplepos_t start, samplepos_t end, double speed, pframes_t nframes, samplecnt_t offset, bool with_auto)
 {
-	// TODO: atomically copy maps & _no_inplace
-	PinMappings in_map (_in_map);
-	PinMappings out_map (_out_map);
-	ChanMapping thru_map (_thru_map);
-	if (_mapping_changed) { // ToDo use a counters, increment until match.
+	if (_mapping_changed) { // ToDo use a counter, increment until match
 		_no_inplace = check_inplace ();
 		_mapping_changed = false;
 	}
+	// TODO: atomically copy maps & _no_inplace
+	PinMappings in_map (_in_map); // TODO Split case below overrides, use const& in_map
+	PinMappings const& out_map (_out_map);
+	ChanMapping const& thru_map (_thru_map);
 
 	if (_latency_changed) {
 		/* delaylines are configured with the max possible latency (as reported by the plugin)
@@ -1081,14 +1081,13 @@ PluginInsert::bypass (BufferSet& bufs, pframes_t nframes)
 	/* bypass the plugin(s) not the whole processor.
 	 * -> use mappings just like connect_and_run
 	 */
-
-	// TODO: atomically copy maps & _no_inplace
-	const ChanMapping in_map (no_sc_input_map ());
-	const ChanMapping out_map (output_map ());
 	if (_mapping_changed) {
 		_no_inplace = check_inplace ();
 		_mapping_changed = false;
 	}
+	// TODO: atomically copy maps & _no_inplace
+	ChanMapping const& in_map (no_sc_input_map ());
+	ChanMapping const& out_map (output_map ());
 
 	bufs.set_count(ChanCount::max(bufs.count(), _configured_internal));
 	bufs.set_count(ChanCount::max(bufs.count(), _configured_out));
@@ -1198,8 +1197,8 @@ PluginInsert::silence (samplecnt_t nframes, samplepos_t start_sample)
 
 	_delaybuffers.flush ();
 
-	ChanMapping in_map (natural_input_streams ());
-	ChanMapping out_map (natural_output_streams ());
+	const ChanMapping in_map (natural_input_streams ());
+	const ChanMapping out_map (natural_output_streams ());
 	ChanCount maxbuf = ChanCount::max (natural_input_streams (), natural_output_streams());
 #ifdef MIXBUS
 	if (is_channelstrip ()) {
@@ -1646,7 +1645,7 @@ PluginInsert::check_inplace ()
 		 *
 		 * but allows     in-port 1 -> sink-pin 2  ||  source-pin 2 -> out port 1
 		 */
-		ChanMapping in_map (input_map ());
+		ChanMapping const& in_map (input_map ());
 		const ChanMapping::Mappings out_m (output_map ().mappings ());
 		for (ChanMapping::Mappings::const_iterator t = out_m.begin (); t != out_m.end () && inplace_ok; ++t) {
 			for (ChanMapping::TypeMapping::const_iterator c = (*t).second.begin (); c != (*t).second.end () ; ++c) {