English Amiga Board - View Single Post - xmaplay - My asm port of FT2's XM replayer for 68020+ Amigas

paraj · 10 November 2022, 19:34

Nice. Tried it with a few modules and seems to sound fine (but I'm not musician). Had a brief look at the source code, and I think you can speed up the mixing code with a relatively simple change. The mixing macros all look more or less like:

Code:

	movem.w	(a3,d2.l*X),d4{/d5}
        ;
	add.w	a4,d7
	addx.l	d1,d2

When unrolled you have a 2-3 (depending on X) cycle "change/use" register stall on d2 (MC68060UM §10.3) . If you move the add/addx sequence a few instructions up (which I think should be possible) it can be avoided.

Probably move.w (...),d4 \ ext.l d4 is also faster than movem.w (..),d4 since ext is (pOEP|sOEP), but would require more changes.

10 November 2022, 19:34	#28
paraj Registered User Join Date: Feb 2017 Location: Denmark Posts: 1,146	Nice. Tried it with a few modules and seems to sound fine (but I'm not musician). Had a brief look at the source code, and I think you can speed up the mixing code with a relatively simple change. The mixing macros all look more or less like: Code: movem.w (a3,d2.l*X),d4{/d5} ; add.w a4,d7 addx.l d1,d2 When unrolled you have a 2-3 (depending on X) cycle "change/use" register stall on d2 (MC68060UM §10.3) . If you move the add/addx sequence a few instructions up (which I think should be possible) it can be avoided. Probably move.w (...),d4 \ ext.l d4 is also faster than movem.w (..),d4 since ext is (pOEP\|sOEP), but would require more changes.