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

Jecel Assumpcao Jr jecel at merlintec.com
Tue Apr 15 18:07:45 UTC 2003


On Tuesday 15 April 2003 14:13, Tim Rowledge wrote:
> Bryce Kampjes <bryce at kampjes.demon.co.uk> 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.

Actually, you could just change the implementation of the "push instance 
variable 3" bytecode from

      push 12[bx]

or whatever nastiness the x86 does, to

      push 11[bx]

since you can think of the OOP as being address+1 and the offset as 4*3.

-- Jecel



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