ya7on/mb8

"Add with carry", "Subtract with borrow" pseudo opcodes

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#85 opened on 2025年12月27日

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説明

To simplify 16-bit arithmetic, it would be useful to introduce ADC/SBC pseudo-opcodes that add or subtract the carry flag from the previous operation.

Currently 16-bit addition requires explicit carry handling

; R0:R1 x (hi:lo)
; R2:R3 y (hi:lo)

ADD R1 R3
JNCR [.no_carry]
INC R0
.no_carry:
ADD R0 R2

With an ADC pseudo opcode the same operation becomes shorter and clearer

ADD R1 R3
ADC R0
ADD R0 R2

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