Sine generator

sine_gen.s

SineGenerate:

	lea	Sine + 8, a0
	move.l	#$7FFF6216, d6	; 2*cos(π/512) >> 2
	move.l	#253, d7
.Loop:
	move.l	-4(a0), d0	; A = sin(i)
	move.l	d6, d1		; B = 2*cos(π/512) >> 2
	move.l	d0, d2
	move.l	d1, d3
	swap	d2			; d2.w = Ah
	swap	d3			; d3.w = Bh
	mulu.w	d2, d1
	lsr.l	#7, d1
	lsr.l	#7, d1		; d1.l = Ah*Bl >> 14
	mulu.w	d3, d0
	lsr.l	#7, d0
	lsr.l	#7, d0		; d0.l = Al*Bh >> 14
	mulu.w	d2, d3
	lsl.l	#2, d3		; d3.l = Ah*Bh << 2
	add.l	d0, d1
	add.l	d3, d1
	sub.l	-8(a0), d1	; sin(i)*2*cos(π/512) - sin(i-1)
	tst.l	(a0)+		; Skip precalculated value
	bne.s	.Skip
	move.l	d1, -4(a0)
.Skip:
	dbf	d7, .Loop
	rts

Sine:
	dc.l	$00000000, $01921F0F	; sin(0), sin(π/512)
	dcb.l	126, 0
	dc.l	$B504F333, $B6206B9E 	; sin(π/4), sin(π/4 + π/512)
	dcb.l	126, 0