Add faster non-alpha version of tile loop

software/apps/tiles_and_sprites/main.c

@@ -73,7 +73,7 @@
 #define MAP_WIDTH  512
 #define MAP_HEIGHT 256
 
-#define N_CHARACTERS 70
+#define N_CHARACTERS 75
 
 typedef struct {
 	int16_t pos_x;
@@ -170,7 +170,7 @@ void render(const game_state_t *gstate) {
 		.log_size_x = 9,
 		.log_size_y = 8,
 		.tilesize = TILESIZE_16,
-		.fill_loop = (tile_loop_t)tile16_16px_alpha_loop
+		.fill_loop = (tile_loop_t)tile16_16px_loop
 	};
 
 	sprite_t sp = {

software/libsprite/tile.S

@@ -44,6 +44,12 @@
 1:
 .endm
 
+.macro do_2px_16bpp rd rs dstoffs
+	strh \rs, [\rd, #\dstoffs]
+	lsrs \rs, #16
+	strh \rs, [\rd, #\dstoffs + 2]
+.endm
+
 // interp0 has been set up to give the next x-ward pointer into the tilemap
 // with each pop. This saves us having to remember the tilemap pointer and
 // tilemap x size mask in core registers.
@@ -53,7 +59,9 @@
 // r2: x0 (start pos in tile space)
 // r3: x1 (end pos in tile space, exclusive)
 
-decl_func tile16_16px_alpha_loop
+// Instantiated with alpha=1 and alpha=0 to get both variants of the loop.
+// Linker garbage collection ensures we only keep the versions we use.
+.macro tile16_16px_loop_alpha_or_nonalpha alpha
 	push {r4-r7, lr}
 	mov r4, r8
 	mov r5, r9
@@ -78,8 +86,10 @@ decl_func tile16_16px_alpha_loop
 	// Fall through into copy loop
 1:
 	ldrh r5, [r4]
+.if \alpha
 	lsrs r6, r5, #ALPHA_SHIFT_16BPP
 	bcc 2f
+.endif
 	strh r5, [r0]
 2:
 	adds r4, #2
@@ -113,6 +123,7 @@ decl_func tile16_16px_alpha_loop
 	lsls r1, #9
 	add r1, r8
 
+.if \alpha
 	ldmia r1!, {r3-r6}
 	do_2px_16bpp_alpha r0 r3 r2 0
 	do_2px_16bpp_alpha r0 r4 r2 4
@@ -123,6 +134,18 @@ decl_func tile16_16px_alpha_loop
 	do_2px_16bpp_alpha r0 r4 r2 20
 	do_2px_16bpp_alpha r0 r5 r2 24
 	do_2px_16bpp_alpha r0 r6 r2 28
+.else
+	ldmia r1!, {r3-r6}
+	do_2px_16bpp r0 r3 0
+	do_2px_16bpp r0 r4 4
+	do_2px_16bpp r0 r5 8
+	do_2px_16bpp r0 r6 12
+	ldmia r1!, {r3-r6}
+	do_2px_16bpp r0 r3 16
+	do_2px_16bpp r0 r4 20
+	do_2px_16bpp r0 r5 24
+	do_2px_16bpp r0 r6 28
+.endif
 	adds r0, 32
 3:
 	cmp r0, ip
@@ -136,8 +159,10 @@ decl_func tile16_16px_alpha_loop
 	b 3f
 1:
 	ldrh r5, [r4]
+.if \alpha
 	lsrs r6, r5, #ALPHA_SHIFT_16BPP
 	bcc 2f
+.endif
 	strh r5, [r0]
 2:
 	adds r4, #2
@@ -150,3 +175,10 @@ decl_func tile16_16px_alpha_loop
 	mov r8, r4
 	mov r9, r5
 	pop {r4-r7, pc}
+.endm
+
+decl_func tile16_16px_alpha_loop
+	tile16_16px_loop_alpha_or_nonalpha 1
+
+decl_func tile16_16px_loop
+	tile16_16px_loop_alpha_or_nonalpha 0

software/libsprite/tile.h

@@ -40,6 +40,7 @@ typedef void (*tile16_loop_t)(uint16_t *dst, const uint16_t *tileset, uint x0, u
 typedef void (*tile8_loop_t)(uint8_t *dst, const uint8_t *tileset, uint x0, uint x1);
 
 void tile16_16px_alpha_loop(uint16_t *dst, const uint16_t *tileset, uint x0, uint x1);
+void tile16_16px_loop(uint16_t *dst, const uint16_t *tileset, uint x0, uint x1);
 
 // ----------------------------------------------------------------------------
 // Functions from tile.c