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cc65/libsrc/common/zerobss.s
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ArmAsm

;
; Ullrich von Bassewitz, 17.09.1998
;
; Zero the bss segment.
;
.export zerobss
.import __BSS_RUN__, __BSS_SIZE__
.importzp ptr1
.code
zerobss:
lda #<__BSS_RUN__
sta ptr1
lda #>__BSS_RUN__
sta ptr1+1
lda #0
tay
; Clear full pages
L1: ldx #>__BSS_SIZE__
beq L3
L2: sta (ptr1),y
iny
bne L2
inc ptr1+1
dex
bne L2
; Clear remaining page (y is zero on entry)
L3: ldx #<__BSS_SIZE__
beq L5
L4: sta (ptr1),y
iny
dex
bne L4
; Done
L5: rts