42 lines
580 B
ArmAsm
42 lines
580 B
ArmAsm
.define Div4
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! This subroutine performs a signed divide on two fourbyte integers.
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! For more detail see dvi.s
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! The only difference is that zeropage locations are twice as big.
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Div4:
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ldy #0
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sty SIGN
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jsr Pop
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stx ARTH
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sta ARTH+1
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jsr Pop
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stx ARTH+2
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sta ARTH+3 ! divisor in ARTH - ARTH+3
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tay
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bpl 1f
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lda #0
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ldx #ARTH
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jsr Ngi4
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ldy #1
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sty SIGN ! it's signed
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1: jsr Pop
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stx ARTH+4
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sta ARTH+5
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jsr Pop
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stx ARTH+6
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sta ARTH+7 ! dividend in ARTH+4 - ARTH+7
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tay
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bpl 1f
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lda #0
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ldx #ARTH+4
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jsr Ngi4
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lda SIGN
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eor #1
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sta SIGN
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lda #1
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sta NBYTES
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1: jmp Duv4
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