; File:   sqrt.s
; Author: Mikael Kalms <mikael@kalms.org>
; Date:   1 Oct 1999
; Title:  Integer square root
;
; Description:
;   Square root calculation, using the sqrt(4*N) = 2*sqrt(N) identity


		section	code,code

; in		d0	x
; out		d0	sqrt(x)

sqrt32
		move.l	d3,-(sp)
		move.l	d2,-(sp)
		move.l	d0,d1
		move.l	#1<<30,d0
		moveq	#32,d2
.iter
		move.l	d0,d3
		rol.l	d2,d3

		add.w	d0,d0
		cmp.l	d3,d1
		blo.s	.skip
		sub.l	d3,d1
		addq.w	#1,d0
.skip
		subq.l	#2,d2
		bhi.s	.iter
		andi.l	#$ffff,d0
		move.l	(sp)+,d2
		move.l	(sp)+,d3
		rts

;sqrt32_old2
;		move.l	d3,-(sp)
;		move.l	d2,-(sp)
;		move.l	d0,d1
;		move.l	#1<<30,d0
;		moveq	#32,d2
;.iter
;		move.l	d0,d3
;		rol.l	d2,d3
;
;		sub.l	d1,d3
;		bhs.s	.skip
;		moveq	#0,d1
;		sub.l	d3,d1
;.skip
;		addx.w	d0,d0
;		subq.l	#2,d2
;		bhi.s	.iter
;		andi.l	#$ffff,d0
;		move.l	(sp)+,d2
;		move.l	(sp)+,d3
;		rts

;sqrt32_old
;		move.l	d3,-(sp)
;		move.l	d2,-(sp)
;		move.l	d0,d1
;		moveq	#0,d0
;		move.l	#$40000000,d2
;.iter
;		move.l	d0,d3
;		add.l	d2,d3
;		lsr.l	#1,d0
;		cmp.l	d3,d1
;		blo.s	.nbit
;		sub.l	d3,d1
;		add.l	d2,d0
;.nbit
;		lsr.l	#2,d2
;		bne.s	.iter
;		move.l	(sp)+,d2
;		move.l	(sp)+,d3
;		rts