pvr: don't use op list to mark block if tile pointer is null

Naomi Doom sets the opaque list block to null in the tile, but op size
in TA_ALLOC_CTRL is non-zero. So use the TR list in this case.

Issue #682

core/hw/pvr/ta.cpp

@@ -467,10 +467,20 @@ static u32 opbSize(int n)
 
 static void markObjectListBlocks()
 {
-	u32 addr = TA_OL_BASE;
+	u32 addr;
+	u32 tile_size;
+	getRegionTileAddrAndSize(addr, tile_size);
+
+	// Read the opaque pointer of the first tile and check that it's non-null (Naomi doom)
+	u32 opbAddr = pvr_read32p<u32>(addr + 4);
+	bool emptyOpaqueList = (opbAddr & 0x80000000) != 0;
+
+	addr = TA_OL_BASE;
 	// opaque
 	u32 opBlockSize = opbSize(TA_ALLOC_CTRL & 3);
-	if (opBlockSize == 0)
+	if (emptyOpaqueList)
+		addr += opBlockSize * (TA_GLOB_TILE_CLIP.tile_y_num + 1) * (TA_GLOB_TILE_CLIP.tile_x_num + 1);
+	if (opBlockSize == 0 || emptyOpaqueList)
 	{
 		// skip modvols OPBs
 		addr += opbSize((TA_ALLOC_CTRL >> 4) & 3) * (TA_GLOB_TILE_CLIP.tile_y_num + 1) * (TA_GLOB_TILE_CLIP.tile_x_num + 1);

core/hw/pvr/ta_ctx.h

@@ -415,6 +415,7 @@ void ta_set_tileclip(u32 tileclip);
 u32 ta_get_list_type();
 void ta_set_list_type(u32 listType);
 void ta_parse_reset();
+void getRegionTileAddrAndSize(u32& address, u32& size);
 
 class TAParserException : public FlycastException
 {

core/hw/pvr/ta_vtx.cpp

@@ -1767,7 +1767,7 @@ void FillBGP(TA_context* ctx)
 	cv[3].v = max_v;
 }
 
-static void getRegionTileAddrAndSize(u32& address, u32& size)
+void getRegionTileAddrAndSize(u32& address, u32& size)
 {
 	address = REGION_BASE;
 	const bool type1_tile = ((FPU_PARAM_CFG >> 21) & 1) == 0;