ack/mach/6500/libem/cmi4.s

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.define Cmi4
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.sect .text
.sect .rom
.sect .data
.sect .bss
.sect .text
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! This subroutine compares on fourbyte integers.
! If T is pushed first and than S, the routine will return:
! -1 if S < T,
! 0 if S = T,
! 1 if S > T.
Cmi4:
jsr Sbi4 ! subtract operands (T - S)
jsr Pop ! get result (lowbyte, lowbyte+1)
stx ARTH ! store lowbyte
sta ARTH+1 ! store lowbyte+1
jsr Pop ! get result (lowbyte+2, lowbyte+3)
tay ! test lowbyte+3
bpl 1f ! S >= T
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lda #0x0FF ! S < T
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tax ! AX becomes -1
rts
1: cmp #0 ! test lowbyte+3 on zero
bne 2f
cpx #0 ! test lowbyte+2 on zero
bne 2f
lda #0
cmp ARTH+1 ! test lowbyte+1 on zero
bne 2f
cmp ARTH ! test lowbyte on zero
bne 2f
lda #0 ! S = T
tax ! AX becomes 0
rts
2: lda #0 ! S > T
ldx #1 ! AX becomes 1
rts