68060-optimised texture mapping – part 1

So, hanging out on the ADA forums, we came up with a conversation about 060-specific optimising, which is sort of like pentium-specific (U/V pipes of fame) optimising. 060 has pretty harsh rules for address generation delays, so there is ample of oportunity to try ingenious ways to reorder stuff as to get no half-cycles wasted… linky linky provided for your pleasure ;)
The only real limitation I can see for this mapper is that the loop count has to be less than 255, but then again I don’t believe in big polygons :P

;
; 8 cycle per 2 pixels 8.16 mapper
; remixed from an ADA thread contributed by
; krishna^scoopex, kalms^the.black.lotus,
; krabob^mankind and winden^network^batman.group
;
; d0 vvUUuuuu		a0 dvDUdudu
; d1 cc--VVvv		a1
; d2 dc--DVdv		a2
; d3 --UUVV-- 0		a3
; d4 --UUVV-- 1		a4
; d5 pixel buffer	a5 tex
; d6			a6 scr
;

.xloop
	move.b	(a5,d3.w),d5	; p1
	move.l	d0,d3		; s1
	move.b	d5,(a6)+	; p2
	move.w	d1,d3		; s2
	lsr.l	#8,d3		; p3
	add.l	a0,d0		; s3
	addx.l	d2,d1		; p4
	move.b	(a5,d4.w),d5	; p5
	move.l	d0,d4		; s5
	move.b	d5,(a6)+	; p6
	move.w	d1,d4		; s6
	lsr.l	#8,d4		; p7
	add.l	a0,d0		; s7
	addx.l	d2,d1		; p8
	bcc	.xloop		; p9 if not predicted, zero if predicted
	rts

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