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57 lines
1.1 KiB
ArmAsm
57 lines
1.1 KiB
ArmAsm
;
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; Ullrich von Bassewitz, 2009-11-04
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; CC65 runtime: 32by16 => 16 unsigned division
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;
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.export udiv32by16r16, 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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udiv32by16r16:
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sta ptr3
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stx ptr3+1
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udiv32by16r16m:
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lda #0
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sta sreg+1
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ldy #32
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L0: asl ptr1
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rol ptr1+1
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rol ptr2
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rol ptr2+1
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rol a
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rol sreg+1
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tax
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cmp ptr3
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lda sreg+1
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sbc ptr3+1
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bcc L1
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sta sreg+1
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txa
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sbc ptr3
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tax
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inc ptr1
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L1: txa
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dey
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bne L0
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sta sreg
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lda ptr1
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ldx ptr1+1
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rts
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