Optimized memset_fast to 25 bytes

memset_fast.asm

; (c) Copyright 2016 Matt Waltz
;-------------------------------------------------------------------------
; Faster memset variation
; Reasons faster:
;  1) uses ldir to memset
;  2) executes in RAM to avoid flash wait states
;-------------------------------------------------------------------------
	.def	_memset_fast
	.assume adl=1

_memset_fast:
	pop	iy
	pop	hl
	pop	de
	pop	bc
	push	bc
	push	de
	push	hl
	push	iy
	dec	bc
	add	hl,bc
	inc	hl
	ret	c
	inc	bc
	cpd
	ld	(hl),e
	ret	po
	push	hl
	pop	de
	dec	de
	lddr
	ret

	end