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35 lines
676 B
ArmAsm
35 lines
676 B
ArmAsm
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; Piotr Fusik, 24.10.2003
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; originally by Ullrich von Bassewitz
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; CC65 runtime: Multiply the primary register by 7
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; Don't touch the Y-register here, the optimizer relies on it!
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.export mulax7
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.importzp ptr1
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.proc mulax7
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sta ptr1
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stx ptr1+1
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asl a
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rol ptr1+1 ; * 2
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asl a
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rol ptr1+1 ; * 4
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asl a
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rol ptr1+1 ; * 8
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sec
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sbc ptr1
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pha
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txa
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eor #$ff
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adc ptr1+1 ; * (8 - 1)
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tax
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pla
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rts
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.endproc
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