wla-dx COMPUTE_PENDING_CALCULATIONS error

linkfile

[objects]
test.o

test.s

.memorymap
slotsize $10000
defaultslot 0
slot 0 $10000
.endme

.rombanksize $10000
.rombanks 1

.bank 0

.org $fffc

.dw Reset ; Emulation mode boot vector

.org $0000

r0: .db 0
r1: .db 0
a0: .db 0
a1: .db 0
t0: .db 0
t1: .db 0
t2: .db 0
t3: .db 0

ballX: .dw 100
ballY: .dw 100
velX: .db 1
velY: .db 1

.org $9800

Reset:

sei
cld
ldx #$ff
txs

lda #100
sta ballX
sta ballY
lda #1
sta velX
sta velY

loop:

lda #$00
jsr PlotBall

lda #$ff
jsr PlotBall

jmp loop

PlotBall: ; Draw A at ballX, ballY

pha

lda ballY
sta a0
lda ballY+1 ; HERE IS THE PROBLEMATIC LINE
sta a1
jsr Mul80

lda r1
clc
adc #$02
sta r1

ldy ballX
pla
sta (r0),y

rts

Mul80: ; Multiply a1:a0 by 80 and put result in r1:r0

; t1:t0 = x << 4, t3:t2 = x << 6
lda a1
asl
asl
asl
asl
sta t1
asl
asl
sta t3
lda a0
lsr
lsr
tax
ora t3
sta t3
txa
lsr
lsr
ora t1
sta t1
lda a0
asl
asl
asl
asl
sta t0
asl
asl
sta t2

; r1:r0 = t1:t0 + t3:t2
lda t0
clc
adc t2
sta r0
lda t1
adc t3
sta r1

rts