| Assembly Source File
| Created 12/12/2006 09:22:59 PM

.xdef ClipGrayDrawTilemap16_fast
.xdef ClipGraySprite16_MASK

ClipGrayDrawTilemap16_fast:
|short x asm("%d0"), short y asm("%d1"), TILEMAP *tilemap asm("%a0"), void *light asm("%a1"), void *dark asm("%a2")


movem.l %d3-%d7/%a2-%a6,-(%sp) |save registers
move.w %d0,%d2
move.w %d1,%d3

lsr.w #4,%d2 |index_x
lsr.w #4,%d3 |index_y

and.w #15,%d0
neg %d0 |-(x&15)

and.w #15,%d1
neg %d1 |-(y&15)

|%d0 and %d1 now hold -(x&15) and -(y&15) respectively, since we no longer need x and y

movea %a0,%a3 |location of tilemap->map
muls.w 12(%a0),%d3 |start_index_y=tilemap->width*index_y;

adda %d3,%a3 
adda %d2,%a3 |%a3 now has the starting index for the first drawn tile of the tilemap

move.w #0,%d2 |%d2 is our vertical loop var (i)
move.w #0,%d3 |%d3 is loop_w
move.w #0,%d4 |%d4 is loop_v


horizontal:
|draw_x=-(x&15)+(loop_w<<4);
move.w %d3,%d5
lsl #4,%d5
add.w %d0,%d5 |%d5=draw_x

move.w %d2,%d5
add.w %d1,%d6 |%d6=draw_y

|matrix_offset=*(map+start_index_y+index_x+loop_v+loop_w);
movea %a3,%a4
adda %d3,%a4
adda %d4,%a4 |address of matrix_offset

move.w (%a4),%d7 |%d6 now holds matrix_offset

/*___Prepare the sprite function___*/
move.l %a2,-(%sp) |void *dark
move.l %a1,-(%sp) |void *light


lsl.w #4,%d7   |matrix_offset<<4
lea 8(%a0),%a5 |%a5 points to tilemap->masks
adda %d7,%a5
move.l %a2,-(%sp) |masks+(matrix_offset<<4)

move.w (%a4),%d7 |%d7 now holds matrix_offset

lsl.w #5,%d7
add.w #16,%d7
lea 4(%a0),%a5
adda %d7,%a5 
move.l %a5,-(%sp) |sprts+(matrix_offset<<5)+16

suba #16,%a5
move.l %a5,-(%sp) |sprts+(matrix_offset<<5)

move.w #16,-(%sp)
move.w %d6,-(%sp)
move.w %d5,-(%sp)


|save registers that will be trashed by the routine
movem.l %d0-%d2/%a0-%a1,-(%sp)

jbsr ClipGraySprite16_MASK |draw the tile
movem.l (%sp)+,%d0-%d2/%a0-%a1 |restore registers

lea 26(%sp),%sp |restore stack pointer


|increment loop vars and test for jumping

addq #1,%d3

cmpi.w #11,%d3
blt horizontal

add.w #16,%d2
add.w 12(%a0),%d4

cmpi.w #8*16,%d2
blt horizontal

movem.l (%sp)+,%d3-%d7/%a2-%a6 |save registers

rts