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36 lines
818 B
ArmAsm

;
; Ullrich von Bassewitz, 26.10.2000
;
; CC65 runtime: Push value in a/x onto the stack
;
.export push0, pusha0, pushax
.importzp sp
push0: lda #0
pusha0: ldx #0
; This function is used *a lot*, so don't call any subroutines here.
; Beware: The value in ax must not be changed by this function!
; Beware^2: The optimizer knows about the value of Y after the function
; returns!
.proc pushax
pha ; (3)
lda sp ; (6)
sec ; (8)
sbc #2 ; (10)
sta sp ; (13)
bcs @L1 ; (17)
dec sp+1 ; (+5)
@L1: ldy #1 ; (19)
txa ; (21)
sta (sp),y ; (27)
pla ; (31)
dey ; (33)
sta (sp),y ; (38)
rts ; (44)
.endproc