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65 lines
1.3 KiB
ArmAsm
65 lines
1.3 KiB
ArmAsm
;
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; Ullrich von Bassewitz, 2009-11-04
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;
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; CC65 runtime: 32by16 => 16 signed division
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;
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.export idiv32by16r16
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.import negax, udiv32by16r16m
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.include "zeropage.inc"
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;---------------------------------------------------------------------------
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; 32by16 division. Divide ptr1:ptr2 by ptr3. Result is in ptr1, remainder
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; in sreg.
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;
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; lhs rhs result result also in remainder
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; -----------------------------------------------------------------------
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; ptr1:ptr2 ptr3 ax ptr1 sreg
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;
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idiv32by16r16:
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stx tmp1
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cpx #0
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bpl @L1
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jsr negax
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@L1: sta ptr3
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stx ptr3+1
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lda ptr2+1
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eor tmp1
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sta tmp1
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bit ptr2+1
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bpl @L3
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; Negate the value in ptr1:ptr2
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ldx #0
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ldy #4
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sec
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@L2: lda ptr1,x
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eor #$FF
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adc #$00
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sta ptr1,x
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inx
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dey
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bne @L2
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; Call the unsigned division routine
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@L3: jsr udiv32by16r16m
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; Check the sign of the result
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bit tmp1
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bmi @L4
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rts
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; Negate the result. We do this here only for the result, not for the
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; remainder!
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@L4: jmp negax
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