Drop dpiece_defs_map_1 memory access optimization

This also gets rid of IsometricCoord. They where used to map tiles in a
way that had a simpler access pattern when rendering the screen in
visual oriented rows.
See
https://github.com/diasurgical/devilution/pull/544#issuecomment-450968761

Source/gendung.cpp

@@ -13,7 +13,6 @@ BYTE *pSpeedCels;
 int nlevel_frames;
 BYTE pdungeon[DMAXX][DMAXY];
 char dDead[MAXDUNX][MAXDUNY];
-MICROS dpiece_defs_map_1[MAXDUNX * MAXDUNY];
 char dPreLight[MAXDUNX][MAXDUNY];
 char TransVal;
 int MicroTileLen;
@@ -334,27 +333,6 @@ void SwapTile(int f1, int f2)
 	level_frame_sizes[f2] = swap;
 }
 
-int IsometricCoord(int x, int y)
-{
-	if (x < MAXDUNY - y)
-		return (y + y * y + x * (x + 2 * y + 3)) / 2;
-
-	x = MAXDUNX - x - 1;
-	y = MAXDUNY - y - 1;
-	return MAXDUNX * MAXDUNY - ((y + y * y + x * (x + 2 * y + 3)) / 2) - 1;
-}
-
-void SetSpeedCels()
-{
-	int x, y;
-
-	for (x = 0; x < MAXDUNX; x++) {
-		for (y = 0; y < MAXDUNY; y++) {
-			dpiece_defs_map_1[IsometricCoord(x, y)] = dpiece_defs_map_2[x][y];
-		}
-	}
-}
-
 void SetDungeonMicros()
 {
 	int i, x, y, lv, blocks;
@@ -389,7 +367,6 @@ void SetDungeonMicros()
 	}
 
 	MakeSpeedCels();
-	SetSpeedCels();
 
 	if (zoomflag) {
 		scr_pix_width = SCREEN_WIDTH;

Source/gendung.h

@@ -13,7 +13,6 @@ extern BYTE *pSpeedCels;
 extern int nlevel_frames;
 extern BYTE pdungeon[DMAXX][DMAXY];
 extern char dDead[MAXDUNX][MAXDUNY];
-extern MICROS dpiece_defs_map_1[MAXDUNX * MAXDUNY];
 extern char dPreLight[MAXDUNX][MAXDUNY];
 extern char TransVal;
 extern int MicroTileLen;
@@ -73,8 +72,6 @@ void FillSolidBlockTbls();
 void MakeSpeedCels();
 void SortTiles(int frames);
 void SwapTile(int f1, int f2);
-int IsometricCoord(int x, int y);
-void SetSpeedCels();
 void SetDungeonMicros();
 void DRLG_InitTrans();
 void DRLG_MRectTrans(int x1, int y1, int x2, int y2);

Source/objects.cpp

@@ -1816,7 +1816,7 @@ void ObjSetMicro(int dx, int dy, int pn)
 
 	dPiece[dx][dy] = pn;
 	pn--;
-	defs = &dpiece_defs_map_1[IsometricCoord(dx, dy)];
+	defs = &dpiece_defs_map_2[dx][dy];
 	if (leveltype != DTYPE_HELL) {
 		v = (WORD *)pLevelPieces + 10 * pn;
 		for (i = 0; i < 10; i++) {
@@ -1839,8 +1839,8 @@ void objects_set_door_piece(int x, int y)
 
 	v1 = *((WORD *)pLevelPieces + 10 * pn + 8);
 	v2 = *((WORD *)pLevelPieces + 10 * pn + 9);
-	dpiece_defs_map_1[IsometricCoord(x, y)].mt[0] = SDL_SwapLE16(v1);
-	dpiece_defs_map_1[IsometricCoord(x, y)].mt[1] = SDL_SwapLE16(v2);
+	dpiece_defs_map_2[x][y].mt[0] = SDL_SwapLE16(v1);
+	dpiece_defs_map_2[x][y].mt[1] = SDL_SwapLE16(v2);
 }
 
 void ObjSetMini(int x, int y, int v)

Source/player.cpp

@@ -967,7 +967,7 @@ void CheckEFlag(int pnum, BOOL flag)
 	x = plr[pnum].WorldX - 1;
 	y = plr[pnum].WorldY + 1;
 	bitflags = 0;
-	pieces = &dpiece_defs_map_1[IsometricCoord(x, y)];
+	pieces = &dpiece_defs_map_2[x][y];
 
 	for (i = 2; i < 10; i++) {
 		bitflags |= pieces->mt[i];
@@ -986,7 +986,7 @@ void CheckEFlag(int pnum, BOOL flag)
 	x = plr[pnum].WorldX;
 	y = plr[pnum].WorldY + 2;
 	bitflags = 0;
-	pieces = &dpiece_defs_map_1[IsometricCoord(x, y)];
+	pieces = &dpiece_defs_map_2[x][y];
 
 	for (i = 2; i < 10; i++) {
 		bitflags |= pieces->mt[i];
@@ -999,7 +999,7 @@ void CheckEFlag(int pnum, BOOL flag)
 	x = plr[pnum].WorldX - 2;
 	y = plr[pnum].WorldY + 1;
 	bitflags = 0;
-	pieces = &dpiece_defs_map_1[IsometricCoord(x, y)];
+	pieces = &dpiece_defs_map_2[x][y];
 
 	for (i = 2; i < 10; i++) {
 		bitflags |= pieces->mt[i];

Source/scrollrt.cpp

@@ -432,7 +432,7 @@ static void scrollrt_draw_e_flag(BYTE *pBuff, int x, int y, int sx, int sy)
 	light_table_index = dLight[x][y];
 	dst = pBuff;
 	cel_transparency_active = (BYTE)(nTransTable[level_piece_id] & TransList[dTransVal[x][y]]);
-	pMap = &dpiece_defs_map_1[IsometricCoord(x, y)];
+	pMap = &dpiece_defs_map_2[x][y];
 
 	arch_draw_type = 1;
 	level_cel_block = pMap->mt[0];
@@ -683,7 +683,6 @@ static void scrollrt_draw(int x, int y, int sx, int sy, int chunks, int dPieceRo
 		chunks++;
 	}
 
-	pMap = &dpiece_defs_map_1[IsometricCoord(x, y)];
 
 	for (j = 0; j < chunks; j++) {
 		if (y >= 0 && y < MAXDUNY && x >= 0 && x < MAXDUNX) {
@@ -691,6 +690,7 @@ static void scrollrt_draw(int x, int y, int sx, int sy, int chunks, int dPieceRo
 			light_table_index = dLight[x][y];
 			if (level_piece_id != 0) {
 				dst = &gpBuffer[sx + sy * BUFFER_WIDTH];
+				pMap = &dpiece_defs_map_2[x][y];
 				cel_transparency_active = (BYTE)(nTransTable[level_piece_id] & TransList[dTransVal[x][y]]);
 				arch_draw_type = 1;
 				level_cel_block = pMap->mt[0];
@@ -722,7 +722,6 @@ static void scrollrt_draw(int x, int y, int sx, int sy, int chunks, int dPieceRo
 		x++;
 		y--;
 		sx += 64;
-		pMap++;
 	}
 }
 

Source/town.cpp

@@ -46,7 +46,7 @@ void town_draw_e_flag(BYTE *pBuff, int x, int y, int capChunks, int sx, int sy)
 	MICROS *pMap;
 
 	dst = pBuff;
-	pMap = &dpiece_defs_map_1[IsometricCoord(x, y)];
+	pMap = &dpiece_defs_map_2[x][y];
 
 	for (i = 0; i < 7; i++) {
 		if (capChunks >= i) {
@@ -154,7 +154,7 @@ void town_draw(int x, int y, int sx, int sy, int chunks, int dPieceRow)
 			level_cel_block = dPiece[x][y];
 			if (level_cel_block != 0) {
 				dst = &gpBuffer[sx + BUFFER_WIDTH * sy];
-				pMap = &dpiece_defs_map_1[IsometricCoord(x, y)];
+				pMap = &dpiece_defs_map_2[x][y];
 				for (i = 0; i < MicroTileLen >> 1; i++) {
 					level_cel_block = pMap->mt[2 * i];
 					if (level_cel_block != 0) {
@@ -190,7 +190,7 @@ void SetTownMicros()
 	for (y = 0; y < MAXDUNY; y++) {
 		for (x = 0; x < MAXDUNX; x++) {
 			lv = dPiece[x][y];
-			pMap = &dpiece_defs_map_1[IsometricCoord(x, y)];
+			pMap = &dpiece_defs_map_2[x][y];
 			if (lv != 0) {
 				lv--;
 				pPiece = (WORD *)&pLevelPieces[32 * lv];