mirror of
https://github.com/pret/pokered.git
synced 2024-10-22 22:55:31 +00:00
143 lines
3.1 KiB
NASM
143 lines
3.1 KiB
NASM
_Multiply::
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ld a, $8
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ld b, a
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xor a
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ldh [hProduct], a
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ldh [hMultiplyBuffer], a
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ldh [hMultiplyBuffer+1], a
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ldh [hMultiplyBuffer+2], a
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ldh [hMultiplyBuffer+3], a
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.loop
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ldh a, [hMultiplier]
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srl a
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ldh [hMultiplier], a ; (aliases: hDivisor, hMultiplier, hPowerOf10)
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jr nc, .smallMultiplier
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ldh a, [hMultiplyBuffer+3]
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ld c, a
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ldh a, [hMultiplicand+2]
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add c
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ldh [hMultiplyBuffer+3], a
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ldh a, [hMultiplyBuffer+2]
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ld c, a
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ldh a, [hMultiplicand+1]
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adc c
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ldh [hMultiplyBuffer+2], a
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ldh a, [hMultiplyBuffer+1]
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ld c, a
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ldh a, [hMultiplicand] ; (aliases: hMultiplicand)
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adc c
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ldh [hMultiplyBuffer+1], a
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ldh a, [hMultiplyBuffer]
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ld c, a
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ldh a, [hProduct] ; (aliases: hProduct, hPastLeadingZeros, hQuotient)
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adc c
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ldh [hMultiplyBuffer], a
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.smallMultiplier
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dec b
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jr z, .done
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ldh a, [hMultiplicand+2]
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sla a
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ldh [hMultiplicand+2], a
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ldh a, [hMultiplicand+1]
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rl a
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ldh [hMultiplicand+1], a
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ldh a, [hMultiplicand]
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rl a
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ldh [hMultiplicand], a
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ldh a, [hProduct]
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rl a
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ldh [hProduct], a
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jr .loop
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.done
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ldh a, [hMultiplyBuffer+3]
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ldh [hProduct+3], a
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ldh a, [hMultiplyBuffer+2]
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ldh [hProduct+2], a
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ldh a, [hMultiplyBuffer+1]
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ldh [hProduct+1], a
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ldh a, [hMultiplyBuffer]
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ldh [hProduct], a
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ret
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_Divide::
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xor a
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ldh [hDivideBuffer], a
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ldh [hDivideBuffer+1], a
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ldh [hDivideBuffer+2], a
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ldh [hDivideBuffer+3], a
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ldh [hDivideBuffer+4], a
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ld a, $9
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ld e, a
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.loop
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ldh a, [hDivideBuffer]
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ld c, a
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ldh a, [hDividend+1] ; (aliases: hMultiplicand)
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sub c
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ld d, a
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ldh a, [hDivisor] ; (aliases: hDivisor, hMultiplier, hPowerOf10)
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ld c, a
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ldh a, [hDividend] ; (aliases: hProduct, hPastLeadingZeros, hQuotient)
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sbc c
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jr c, .next
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ldh [hDividend], a ; (aliases: hProduct, hPastLeadingZeros, hQuotient)
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ld a, d
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ldh [hDividend+1], a ; (aliases: hMultiplicand)
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ldh a, [hDivideBuffer+4]
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inc a
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ldh [hDivideBuffer+4], a
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jr .loop
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.next
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ld a, b
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cp $1
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jr z, .done
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ldh a, [hDivideBuffer+4]
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sla a
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ldh [hDivideBuffer+4], a
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ldh a, [hDivideBuffer+3]
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rl a
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ldh [hDivideBuffer+3], a
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ldh a, [hDivideBuffer+2]
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rl a
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ldh [hDivideBuffer+2], a
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ldh a, [hDivideBuffer+1]
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rl a
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ldh [hDivideBuffer+1], a
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dec e
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jr nz, .next2
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ld a, $8
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ld e, a
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ldh a, [hDivideBuffer]
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ldh [hDivisor], a ; (aliases: hDivisor, hMultiplier, hPowerOf10)
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xor a
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ldh [hDivideBuffer], a
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ldh a, [hDividend+1] ; (aliases: hMultiplicand)
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ldh [hDividend], a ; (aliases: hProduct, hPastLeadingZeros, hQuotient)
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ldh a, [hDividend+2]
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ldh [hDividend+1], a ; (aliases: hMultiplicand)
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ldh a, [hDividend+3]
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ldh [hDividend+2], a
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.next2
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ld a, e
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cp $1
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jr nz, .okay
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dec b
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.okay
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ldh a, [hDivisor] ; (aliases: hDivisor, hMultiplier, hPowerOf10)
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srl a
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ldh [hDivisor], a ; (aliases: hDivisor, hMultiplier, hPowerOf10)
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ldh a, [hDivideBuffer]
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rr a
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ldh [hDivideBuffer], a
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jr .loop
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.done
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ldh a, [hDividend+1] ; (aliases: hMultiplicand)
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ldh [hRemainder], a ; (aliases: hDivisor, hMultiplier, hPowerOf10)
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ldh a, [hDivideBuffer+4]
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ldh [hQuotient+3], a
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ldh a, [hDivideBuffer+3]
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ldh [hQuotient+2], a
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ldh a, [hDivideBuffer+2]
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ldh [hQuotient+1], a ; (aliases: hMultiplicand)
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ldh a, [hDivideBuffer+1]
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ldh [hDividend], a ; (aliases: hProduct, hPastLeadingZeros, hQuotient)
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ret
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