41 lines
729 B
ArmAsm
41 lines
729 B
ArmAsm
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.define Sri2, Sru2
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! The subroutine Sri2 shifts a signed integer n times right.
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! In the case of a negative integer there is signextension.
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! The subroutine Sru2 shifts right an unsigned integer.
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! The returned value is in registerpair AX.
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Sru2:
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txa
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bne 1f
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jmp Pop ! zero shift, return input
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1: tay
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jsr Pop ! get integer
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stx Ytmp ! save lowbyte
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jmp 2f ! shift unsigned
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Sri2:
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txa
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bne 1f
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jmp Pop ! zero shift, return input
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1: tay
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jsr Pop ! get integer
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stx Ytmp ! save lowbyte
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tax
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bmi 1f ! negative signextended shift
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2: lsr a
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ror Ytmp ! shift not signextended
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dey
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bne 2b
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ldx Ytmp ! get lowbyte
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rts
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1: sec ! shift signextended
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ror a
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ror Ytmp
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dey
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bne 1b
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ldx Ytmp ! get lowbyte
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rts
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