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Add TODO note.

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Chris Pressey 2018-04-18 17:59:42 +01:00
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@ -75,6 +75,15 @@ TODO
To turn `word` type into `byte`.
Trying to remember if we have a compelling case for this or now. The best I can think
of is for implementing 16-bit `cmp` in an efficient way. Maybe we should see if we
can get by with 16-bit `cmp` instead though.
The problem is that once a byte is extracted, putting it back into a word is awkward.
The address operators have to modify a destination in a special way. That is, when
you say `st a, >word`, you are updating `word` to be `word & $ff | a << 8`, somelike.
Is that consistent with `st`? Well, probably it is, but we have to explain it.
### Save registers on stack
This preserves them, so that, semantically, they can be used later even though they