Keep DAA! (was Re: 8086 bugs)

[der Mouse]

>> Now, how about lowercase hex (a-f instead of A-F)?  Adjusting by 39
>> instead of 7 would be a sufficient pain that I do not consider this
>> algorithm suitable.
> You don't need to, just OR the result with $20.

Grr, that's annoying.  Here I was trying to come up with a way to do
conditional arithemtic in a single register without conditionals, and
you point out it's unnecessary.  I was close, too - using rotates
through the carry and then instructions like SBI $00.  I think it's
possible, though it needs lots of rotates.  (Sequences like: use Dave
Dunfield's code up through the second-last instruction (SBI $09), then
SBI $F5; RLC; RLC; RLC; RLC; SBI $00; RRC; RRC; RRC; RRC.  That gives
too wide a gap, but I think it could be modified into the kind of
solution I was thinking about.)

Still, it was fun to work on.  Trying to do things in a ridiculously
constrained environment (like conditional arithmetic without
conditionals) can be fun.

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