VarAction2: Re-use allocated callback result sprite groups

src/newgrf.cpp

@@ -79,6 +79,8 @@ const std::vector<GRFFile *> &GetAllGRFFiles()
 	return _grf_files;
 }
 
+static btree::btree_map<uint16, const CallbackResultSpriteGroup *> _callback_result_cache;
+
 /** Miscellaneous GRF features, set by Action 0x0D, parameter 0x9E */
 byte _misc_grf_features = 0;
 
@@ -5522,13 +5524,24 @@ static void SkipAct1(ByteReader *buf)
 	grfmsg(3, "SkipAct1: Skipping %d sprites", _cur.skip_sprites);
 }
 
+static const CallbackResultSpriteGroup *NewCallbackResultSpriteGroup(uint16 groupid)
+{
+	uint16 result = CallbackResultSpriteGroup::TransformResultValue(groupid, _cur.grffile->grf_version >= 8);
+
+	const CallbackResultSpriteGroup *&ptr = _callback_result_cache[result];
+	if (ptr == nullptr) {
+		assert(CallbackResultSpriteGroup::CanAllocateItem());
+		ptr = new CallbackResultSpriteGroup(result);
+	}
+	return ptr;
+}
+
 /* Helper function to either create a callback or link to a previously
  * defined spritegroup. */
 static const SpriteGroup *GetGroupFromGroupID(byte setid, byte type, uint16 groupid)
 {
 	if (HasBit(groupid, 15)) {
-		assert(CallbackResultSpriteGroup::CanAllocateItem());
-		return new CallbackResultSpriteGroup(groupid, _cur.grffile->grf_version >= 8);
+		return NewCallbackResultSpriteGroup(groupid);
 	}
 
 	if (groupid > MAX_SPRITEGROUP || _cur.spritegroups[groupid] == nullptr) {
@@ -5576,8 +5589,7 @@ static const SpriteGroup *GetGroupByID(uint16 groupid)
 static const SpriteGroup *CreateGroupFromGroupID(byte feature, byte setid, byte type, uint16 spriteid)
 {
 	if (HasBit(spriteid, 15)) {
-		assert(CallbackResultSpriteGroup::CanAllocateItem());
-		return new CallbackResultSpriteGroup(spriteid, _cur.grffile->grf_version >= 8);
+		return NewCallbackResultSpriteGroup(spriteid);
 	}
 
 	if (!_cur.IsValidSpriteSet(feature, spriteid)) {
@@ -11195,6 +11207,7 @@ void ResetNewGRFData()
 
 	InitializeSoundPool();
 	_spritegroup_pool.CleanPool();
+	_callback_result_cache.clear();
 }
 
 /**
@@ -12443,6 +12456,7 @@ void LoadNewGRF(uint load_index, uint num_baseset)
 	for (GRFFile * const file : _grf_files) {
 		file->string_map.clear();
 	}
+	_callback_result_cache.clear();
 
 	/* Call any functions that should be run after GRFs have been loaded. */
 	AfterLoadGRFs();

src/newgrf_spritegroup.cpp

@@ -259,7 +259,7 @@ const SpriteGroup *DeterministicSpriteGroup::Resolve(ResolverObject &object) con
 	if (this->calculated_result) {
 		/* nvar == 0 is a special case -- we turn our value into a callback result */
 		if (value != CALLBACK_FAILED) value = GB(value, 0, 15);
-		static CallbackResultSpriteGroup nvarzero(0, true);
+		static CallbackResultSpriteGroup nvarzero(0);
 		nvarzero.result = value;
 		return &nvarzero;
 	}

src/newgrf_spritegroup.h

@@ -369,19 +369,25 @@ protected:
 struct CallbackResultSpriteGroup : SpriteGroup {
 	/**
 	 * Creates a spritegroup representing a callback result
+	 * @param result The result as returned from TransformResultValue
+	 */
+	CallbackResultSpriteGroup(uint16 result) :
+		SpriteGroup(SGT_CALLBACK),
+		result(result) {}
+
+	/**
+	 * Transforms a callback result value
 	 * @param value The value that was used to represent this callback result
 	 * @param grf_version8 True, if we are dealing with a new NewGRF which uses GRF version >= 8.
 	 */
-	CallbackResultSpriteGroup(uint16 value, bool grf_version8) :
-		SpriteGroup(SGT_CALLBACK),
-		result(value)
+	static uint16 TransformResultValue(uint16 value, bool grf_version8)
 	{
 		/* Old style callback results (only valid for version < 8) have the highest byte 0xFF so signify it is a callback result.
 		 * New style ones only have the highest bit set (allows 15-bit results, instead of just 8) */
-		if (!grf_version8 && (this->result >> 8) == 0xFF) {
-			this->result &= ~0xFF00;
+		if (!grf_version8 && (value >> 8) == 0xFF) {
+			return value & ~0xFF00;
 		} else {
-			this->result &= ~0x8000;
+			return value & ~0x8000;
 		}
 	}