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cc65/libsrc/runtime/mulax9.s

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;
; Piotr Fusik, 24.10.2003
; originally by Ullrich von Bassewitz
;
; CC65 runtime: Multiply the primary register by 9
;
.export mulax9
.importzp ptr1
.proc mulax9
sta ptr1
stx ptr1+1
asl a
rol ptr1+1 ; * 2
asl a
rol ptr1+1 ; * 4
asl a
rol ptr1+1 ; * 8
clc
adc ptr1 ; * (8+1)
pha
txa
adc ptr1+1
tax
pla
rts
.endproc