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slightly faster swapzp, and some comments

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4am 2020-09-04 19:25:05 -04:00
parent 39b643de50
commit 3dfc71a25a
3 changed files with 43 additions and 40 deletions
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7
src/fx/fx.hgr.1bit.fizzle.a
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@ -8,7 +8,7 @@
copymasks = $6100 ; [256 bytes, page-aligned]
addrs = $6200 ; [256 bytes, page-aligned]
jsr swapzp ; copy LFSR code to zerp page
jsr swapzp ; copy LFSR code to zero page
inx
lda #1 ; create copymask lookup table
@ -62,14 +62,15 @@ src eor $FD00, y ; merge source and destination bits
and copymasks, x ; isolate the bits to replace, zero the rest
eor (<dst+1), y ; unmerge source and destination bits, leaves 'to keep' destination bits intact
dst sta $FD00, y ; write the result
txa
lsr
tax
tya
ror
tay
bcc loop2 ; C set by ror
bne loop ; Z set by tay
bcc loop2 ; C modified by ror
bne loop ; Z modified by tay
bit $C000
bmi exit
txa

54
src/fx/fx.hgr.2bit.fizzle.a
View File

@ -5,12 +5,13 @@
!to "build/FX/BIT2.FIZZLE",plain
*=$6000
addrs = $6100 ; [256 bytes]
copymasks = $6200 ; [128 bytes]
addrs = $6100 ; [256 bytes, page-aligned]
copymasks = $6200 ; [128 bytes, should not cross page boundary]
jsr swapzp ; copy LFSR code to zero page
jsr swapzp
ldx #0
lda #%00000011
lda #%00000011 ; create copymask lookup table
-- ldy #$20
ora #%10000000
- sta copymasks, x
@ -22,7 +23,7 @@ copymasks = $6200 ; [128 bytes]
bne --
clc
ldx #0
-- ldy #$20
-- ldy #$20 ; create address lookup table
tya
- sta addrs, x
adc #1
@ -31,14 +32,17 @@ copymasks = $6200 ; [128 bytes]
bne -
txa
bne --
jsr $0
jsr $0 ; call LFSR code on zero page
lda $4000 ; last lousy byte (because LFSR never hits 0)
sta $2000
; fall through to restore and exit
swapzp ldx #(end-start-1)
- lda $0, x
pha
lda start, x
sta $0, x
pla
- ldy start, x
lda $0, x
sta start, x
sty $0, x
dex
bpl -
rts
@ -47,31 +51,31 @@ start
!pseudopc 0 {
; in: X,Y=0
loop txa
loop1 eor #$60
tax
loop2 lda addrs, x
sta <dst+2
eor #$60
loop1 eor #$60 ; LFSR form 0x6000 with period 32767
tax ; X is LFSR high byte, Y is LFSR low byte
loop2 lda addrs, x ; which means X is the index into the base address lookup table
sta <dst+2 ; and Y is the offset from the base address
eor #$60 ; which works out well with the available addressing modes
sta <src+2
lda (<dst+1), y
src eor $FD00, y
and copymasks, x
eor (<dst+1), y
dst sta $FD00, y
src eor $FD00, y ; merge source and destination bits
and copymasks, x ; isolate the bits to replace, zero the rest
eor (<dst+1), y ; unmerge source and destination bits, leaves 'to keep' destination bits intact
dst sta $FD00, y ; write the result
txa
lsr
tax
tya
ror
tay
bcc loop2
bne loop
bcc loop2 ; C modified by ror
bne loop ; Z modified by tay
bit $C000
bmi exit
txa
bne loop1
exit lda $4000
sta $2000
rts
exit rts
}
end

8
src/fx/fx.shr.fizzle.a
View File

@ -36,12 +36,10 @@ addrs=$A100 ; [128 bytes, can be anywhere in main memory but don't
sta $C004 ; restore and exit
swapzp ldx #(end-start-1)
- lda $0, x
pha
lda start, x
sta $0, x
pla
- ldy start, x
lda $0, x
sta start, x
sty $0, x
dex
bpl -
rts