40 lines
542 B
ArmAsm
40 lines
542 B
ArmAsm
.define Ror4
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.sect .text
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.sect .rom
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.sect .data
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.sect .bss
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.sect .text
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! This subroutine rotates right a fourbyte word.
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! The number of rotates is in X.
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Ror4:
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txa
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bne 1f ! a zero rotate skip
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rts
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1: tay
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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
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2: lsr ARTH+3 ! rotate word
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ror ARTH+2
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ror ARTH+1
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ror ARTH
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bcc 1f ! no carry
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lda #0x80 ! put carry in leftmost bit
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ora ARTH+3
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sta ARTH+3
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1: dey
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bne 2b
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lda ARTH+3
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ldx ARTH+2
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jsr Push
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lda ARTH+1
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ldx ARTH
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jmp Push ! push result onto the stack
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