tomaitheous

  ; ((x/8) * map_height)+(y/8)

  ; d0=  object #
  ; a1=  X coords array (fixed reg for multiple calls)
  ; a2=  Y coords array (fixed reg for multiple calls)
  ; a3=  shift+mul LUT
  ; a4=  relative starting point of map in circular buffer
  ; d2=  temp
  ; a0=  temp



  moveq     #0,d1             ;4   clear upper reg for building complete address pointer
  moveq     #0,a0             ;4   clear upper range for unsigned indexing
  move.w    0(a1,d0.l),d1     ;14
  lsl.w     #1,d1             ;8
  movea.w   d1,a0             ;4   a0=x_array[d0]<<1;
  move.w    0(a2,d0.l),d1     ;14
  lsr.w     #$03,d1           ;12  d1=y_array[d0]/8;
  add.w     0(a3,a0.l),d1     ;14  d1+=shift_mul_array[a0];
  add.l     a4,d1             ;8   d1+=relative_start_point
  andi.w    #$f7ff,d1         ;8   clip to wrap with buffer
  movea.l   d1,a3             ;4   a3 is now x/y position of map
  addi.w    #col_len,d1       ;8   add a columns worth of bytes to get into the next column
  andi.w    #$f7ff,d1         ;8   clip to wrap with buffer
  movea.l   d2,a4             ;4   a3 is now x/y+1 position of map
  move.w    (a4),d2           ;8
  or.w      (a3),d2           ;8   set Z flag according all four tiles
  rts                         ;16

                      ;146 cycles         17 instructions





  ; (x>>3 * map_width)+y>>3
  ; _X=  x pixel offset array of objects
  ; _Y=  y pixel offset array of objects
  ; r2=  map column offset
  ; tbl= shift+multiply LUT for column offset
  ; Reg X is the pointer/index to object's positions*

  ldy <_Y,x               ;4
  lda shift_lut,y         ;5        y>>3
  ldy <_X,x               ;4
  clc                     ;2
  adc tbl.l,y             ;5
  adc <r2.l               ;4
  sta <r0.l               ;4
  tax                     ;2
  lda tbl.h,y             ;5
  adc <r2.h               ;4
  and #bffr_width         ;2
  sta <r0.h               ;4
  sax                     ;3
  adc #col_width          ;2
  sta <r1.l               ;4
  txa                     ;2
  adc #$00                ;2
  and #bffr_width         ;2
  sta <r1.h               ;4
  lda [r0]                ;7
  ora [r1]                ;7
  ldy #$01                ;2
  ora [r0],y              ;7
  ora [r1],y              ;7
  rts                     ;7

                  ;101 cycles   25 instructions






  ldy <_Y,x               ;4
  lda shift_lut,y         ;5
  lda <_X,x               ;4
  asl a                   ;2
  tay                     ;2
  clc                     ;2
  adc tbl,y               ;5
  adc <r2                 ;4
  and #bffr_width         ;3
  sta <r0                 ;4
  adc #col_width          ;3
  and #bffr_width         ;3
  sta <r1                 ;4
  lda [r0]                ;6
  ora [r1]                ;6
  rts                     ;6

                  ;63 cycles   16 instructions