2009/3/15 Hans-Martin Mosner <hmm at heeg.de>

> nicolas cellier schrieb:
> > Hans,
> > Tagging/untagging could be very fast! See my other post
> >
> > 1) UnTagging a double= No op
> > 2) Tagging a double= a isnan test (so as to have a representable nan
> > in Smalltalk)
> > 3) This trick does not had any extra cost to tagging/untagging of
> > other oops
> That's true for a 64-bit processor, and on such hardware I see the
> advantages of this scheme.
> For 32-bit hardware, it won't work.
> Hopefully we'll all have suitable hardware in the near future...
> But for example, I'm running 32-bit linux here on my 64-bit AMD
> processor just because the WLAN card I'm using only has a 32-bit Windows
> driver, and ndiswrapper on 64-bit linux would require a 64-bit driver to
> work correctly (which is somewhat stupid IMHO but I'm not going to hack
> ndiswrapper).
> In the real world, there are tons of silly constraints like this which
> still prevent people from fully using 64-bit hardware.
>
> Cheers,
> Hans-Martin
>

Of course, most of the nice properties come from the 64 bits adressing...
Hey, wait, I don't even have a 64 processor in my house!
For the fun I imagine we could emulate by spanning each oop over two int32
typedef struct {int32 high,low;} oop;
I would expect a slower VM by roughly a factor 2 - except for double
arithmetic...

Nicolas
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