Only run trace restrict programs if they contain relevant actions.

Only run in pathfinder case if deny or penalty are present.
Only run in is safe waiting tile case is reserve through is present.
Presence is determined at program validation time and cached in the
program structure.
Validator now checks for unknown non-conditional instructions.

src/lang/english.txt

@@ -2462,6 +2462,7 @@ STR_TRACE_RESTRICT_ERROR_VALIDATE_END_CONDSTACK                 :Validation fail
 STR_TRACE_RESTRICT_ERROR_VALIDATE_NO_IF                         :Validation failed: else/endif without opening if
 STR_TRACE_RESTRICT_ERROR_VALIDATE_DUP_ELSE                      :Validation failed: duplicate else
 STR_TRACE_RESTRICT_ERROR_VALIDATE_ELIF_NO_IF                    :Validation failed: else if without opening if
+STR_TRACE_RESTRICT_ERROR_VALIDATE_UNKNOWN_INSTRUCTION           :Validation failed: unknown instruction
 STR_TRACE_RESTRICT_ERROR_SOURCE_SAME_AS_TARGET                  :Source and target signals are the same
 STR_TRACE_RESTRICT_ERROR_CAN_T_RESET_SIGNAL                     :{WHITE}Can't reset signal
 STR_TRACE_RESTRICT_ERROR_CAN_T_COPY_PROGRAM                     :{WHITE}Can't copy program

src/pathfinder/yapf/yapf_costrail.hpp

@@ -264,7 +264,7 @@ private:
 	inline bool ExecuteTraceRestrict(Node& n, TileIndex tile, Trackdir trackdir, int& cost, TraceRestrictProgramResult &out)
 	{
 		const TraceRestrictProgram *prog = GetExistingTraceRestrictProgram(tile, TrackdirToTrack(trackdir));
-		if (prog) {
+		if (prog && prog->actions_used_flags & TRPAUF_PF) {
 			prog->Execute(Yapf().GetVehicle(), TraceRestrictProgramInput(tile, trackdir, &TraceRestrictPreviousSignalCallback, &n), out);
 			if (out.flags & TRPRF_DENY) {
 				n.m_segment->m_end_segment_reason |= ESRB_DEAD_END;

src/pbs.cpp

@@ -468,7 +468,7 @@ bool IsSafeWaitingPosition(const Train *v, TileIndex tile, Trackdir trackdir, bo
 		if (HasPbsSignalOnTrackdir(ft.m_new_tile, td)) {
 			if (IsRestrictedSignal(ft.m_new_tile)) {
 				const TraceRestrictProgram *prog = GetExistingTraceRestrictProgram(ft.m_new_tile, TrackdirToTrack(td));
-				if (prog) {
+				if (prog && prog->actions_used_flags & TRPAUF_RESERVE_THROUGH) {
 					TraceRestrictProgramResult out;
 					prog->Execute(v, TraceRestrictProgramInput(tile, trackdir, &IsSafeWaitingPositionTraceRestrictPreviousSignalCallback, nullptr), out);
 					if (out.flags & TRPRF_RESERVE_THROUGH) {

src/tracerestrict.cpp

@@ -413,12 +413,14 @@ void TraceRestrictProgram::DecrementRefCount() {
 /**
  * Validate a instruction list
  * Returns successful result if program seems OK
- * This only validates that conditional nesting is correct, at present
+ * This only validates that conditional nesting is correct,
+ * and that all non-conditionals have a known type, at present
  */
-CommandCost TraceRestrictProgram::Validate(const std::vector<TraceRestrictItem> &items) {
+CommandCost TraceRestrictProgram::Validate(const std::vector<TraceRestrictItem> &items, TraceRestrictProgramActionsUsedFlags &actions_used_flags) {
 	// static to avoid needing to re-alloc/resize on each execution
 	static std::vector<TraceRestrictCondStackFlags> condstack;
 	condstack.clear();
+	actions_used_flags = static_cast<TraceRestrictProgramActionsUsedFlags>(0);
 
 	size_t size = items.size();
 	for (size_t i = 0; i < size; i++) {
@@ -462,6 +464,19 @@ CommandCost TraceRestrictProgram::Validate(const std::vector<TraceRestrictItem>
 					return_cmd_error(STR_TRACE_RESTRICT_ERROR_OFFSET_TOO_LARGE); // instruction ran off end
 				}
 			}
+			switch (GetTraceRestrictType(item)) {
+				case TRIT_PF_DENY:
+				case TRIT_PF_PENALTY:
+					actions_used_flags |= TRPAUF_PF;
+					break;
+
+				case TRIT_RESERVE_THROUGH:
+					actions_used_flags |= TRPAUF_RESERVE_THROUGH;
+					break;
+
+				default:
+					return_cmd_error(STR_TRACE_RESTRICT_ERROR_VALIDATE_UNKNOWN_INSTRUCTION);
+			}
 		}
 	}
 	if(!condstack.empty()) {
@@ -887,7 +902,8 @@ CommandCost CmdProgramSignalTraceRestrict(TileIndex tile, DoCommandFlag flags, u
 			break;
 	}
 
-	CommandCost validation_result = TraceRestrictProgram::Validate(items);
+	TraceRestrictProgramActionsUsedFlags actions_used_flags;
+	CommandCost validation_result = TraceRestrictProgram::Validate(items, actions_used_flags);
 	if (validation_result.Failed()) {
 		return validation_result;
 	}
@@ -897,6 +913,7 @@ CommandCost CmdProgramSignalTraceRestrict(TileIndex tile, DoCommandFlag flags, u
 
 		// move in modified program
 		prog->items.swap(items);
+		prog->actions_used_flags = actions_used_flags;
 
 		if (prog->items.size() == 0 && prog->refcount == 1) {
 			// program is empty, and this tile is the only reference to it

src/tracerestrict.h

@@ -197,6 +197,15 @@ enum TraceRestrictProgramResultFlags {
 };
 DECLARE_ENUM_AS_BIT_SET(TraceRestrictProgramResultFlags)
 
+/**
+ * Enumeration for TraceRestrictProgram::actions_used_flags
+ */
+enum TraceRestrictProgramActionsUsedFlags {
+	TRPAUF_PF                     = 1 << 0,  ///< Pathfinder deny or penalty are present
+	TRPAUF_RESERVE_THROUGH        = 1 << 1,  ///< Reserve through action is present
+};
+DECLARE_ENUM_AS_BIT_SET(TraceRestrictProgramActionsUsedFlags)
+
 /**
  * Execution input of a TraceRestrictProgram
  */
@@ -230,9 +239,10 @@ struct TraceRestrictProgramResult {
 struct TraceRestrictProgram : TraceRestrictProgramPool::PoolItem<&_tracerestrictprogram_pool> {
 	std::vector<TraceRestrictItem> items;
 	uint32 refcount;
+	TraceRestrictProgramActionsUsedFlags actions_used_flags;
 
 	TraceRestrictProgram()
-			: refcount(0) { }
+			: refcount(0), actions_used_flags(static_cast<TraceRestrictProgramActionsUsedFlags>(0)) { }
 
 	void Execute(const Train *v, const TraceRestrictProgramInput &input, TraceRestrictProgramResult &out) const;
 
@@ -243,7 +253,7 @@ struct TraceRestrictProgram : TraceRestrictProgramPool::PoolItem<&_tracerestrict
 
 	void DecrementRefCount();
 
-	static CommandCost Validate(const std::vector<TraceRestrictItem> &items);
+	static CommandCost Validate(const std::vector<TraceRestrictItem> &items, TraceRestrictProgramActionsUsedFlags &actions_used_flags);
 
 	static size_t InstructionOffsetToArrayOffset(const std::vector<TraceRestrictItem> &items, size_t offset);
 
@@ -285,10 +295,11 @@ struct TraceRestrictProgram : TraceRestrictProgramPool::PoolItem<&_tracerestrict
 		return items.begin() + TraceRestrictProgram::InstructionOffsetToArrayOffset(items, instruction_offset);
 	}
 
-	/**
+	/** Call validation function on current program instruction list and set actions_used_flags */
-	 * Call validation function on current program instruction list
+	CommandCost Validate()
-	 */
+	{
-	CommandCost Validate() const { return TraceRestrictProgram::Validate(items); }
+		return TraceRestrictProgram::Validate(items, actions_used_flags);
+	}
 };
 
 /** Get TraceRestrictItem type field */

src/tracerestrict_gui.cpp

@@ -1680,7 +1680,8 @@ private:
 			items.insert(items.begin() + array_offset, item);
 		}
 
-		return TraceRestrictProgram::Validate(items).Succeeded();
+		TraceRestrictProgramActionsUsedFlags actions_used_flags;
+		return TraceRestrictProgram::Validate(items, actions_used_flags).Succeeded();
 	}
 
 	/**