VI4 (was: RE: [ANN]Draft rough plan for 3.6!)

Tim Rowledge tim at
Tue Apr 15 17:13:39 UTC 2003

Bryce Kampjes <bryce at> wrote:

> There are a few things that would be nice purely for performance in an
> image change. Having a tag bit of 0 rather than 1 for integers would
> shave 3 instructions off simple arithmetic taking it down to 5
> instructions on an x86.
.. and it would involve having the tag bit added to every OOP, meaning
that one would have to mask out that bit for any indirection through
that OOP. 

> Is it possible to speed proper block closures up using less drastic
> measures?
Of course. Not that it's particularly tied to block or closures but a
realtively simple context cache (Eliot wrote one design up for OOPSLA87)
can make a big difference. Costs some memory of course but that is
something that can be configured at VM compile time or start time
depending on the design. The key point is to not break the rules; one of
the objections to Anthony's first BC system was that it did that by
making too much visible and different.

Tim Rowledge, tim at,
Useful random insult:- Ready to join the Anti-Mensa Society.

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