English Amiga Board - View Single Post - Optimizing the 68020+ 32-bit math

a/b · 29 April 2021, 12:20

Why didn't you use "the same" algorithm, something like (code not tested)?

Code:

	move.l	d4,d0
	swap	d0
	cmp.l	d0,d6		; divident >= (divisor<<16)?
	bhs.b	.32bit

.16bit	divu.w	d4,d6
	swap	d6
	move.w	d6,(a3)

.32bit	divul.l	d4,d7:d6
	move.w	d7,(a3)

edit: To keep it simple: do a faster (32/16) div whenever possible *without* penalty of failing (it's still a slooow div), extra check is compensated for.

29 April 2021, 12:20	#6
a/b Registered User Join Date: Jun 2016 Location: europe Posts: 1,039	Why didn't you use "the same" algorithm, something like (code not tested)? Code: move.l d4,d0 swap d0 cmp.l d0,d6 ; divident >= (divisor<<16)? bhs.b .32bit .16bit divu.w d4,d6 swap d6 move.w d6,(a3) .32bit divul.l d4,d7:d6 move.w d7,(a3) edit: To keep it simple: do a faster (32/16) div whenever possible without penalty of failing (it's still a slooow div), extra check is compensated for. Last edited by a/b; 29 April 2021 at 13:15.