Re: Best tools for writing an assembler?

glen herrmannsfeldt schrieb:


> There are some interesting cases where the instruction choice (and
> length) depends on the size of an address, which (in the case of a
> forward reference) depends on the instruction length. If you can
> avoid that, it is pretty easy.
>
> -- glen
> [Variable length instructions aren't that hard. You start by assuming
> everything will be the long form, then iterate over the code a few
> times shrinking what you can. That isn't always perfectly optimal
> (which is known to be NP complete), but it's pretty close. -John]


Hmm, I'd start with the *shortest* encoding, and extend whatever doesn't
fit afterwards. This avoids "deadlocks", resulting from kind of circular
references. Indeed harder is reordering parts of the code, in order to
reduce the number of long references - kind of "travelling salesman"
problem?


DoDi

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