🚀 go-pugleaf

In article <ARS4N0F@xds13.ferranti.com> peter@ficc.ferranti.com (Peter da Silva) writes:
>> Regarding the merits of assigned GOTO, consider an architecture where the
>> address of an instruction cannot in fact be stored in an INTEGER variable
>> (because, for example, an address has 64 bits whereas an integer has 32).
>
>Given the relatively small number of addresses involved, using a lookup
>table and a small integer token for each numbered line is an easy solution
>to this problem.

Sure.  Another alternative would be to use relative offsets from the
beginning of the routine (not from the ASSIGN point!).  32 bits should
cover most routines :-)

I think the real problem with label variables is the tangle they make
of the flow graph.  The poor ol' optimizer sees a "GOTO lvar" and
says "Well, I guess he can branch to any label?"  We can do better by
noticing which labels participate in ASSIGN statements, but it's
still a mess.  Nice programmers (who'd like the optimizer to be
nice to them) will provide a list of alternatives on their assigned gotos.

--
Preston Briggs				looking for the great leap forward
preston@titan.rice.edu