Re: Break 2.4 VM in five easy steps

Maciej Zenczykowski (maze@druid.if.uj.edu.pl)
Mon, 11 Jun 2001 14:06:14 +0200 (CEST)


On Fri, 8 Jun 2001, Pavel Machek wrote:

> That modulo is likely slower than dereference.
>
> > + if (count % 256 == 0) {

You are forgetting that this case should be converted to and 255 or a
plain byte reference by any optimizing compiler - and gcc surely is,
on x86 this code can be reduced to around 2 cycles (Pentium: mov, or, jnz,
with preceding code intertwined to cancel stalls and jnz being likely in
the code buffer)...

Maciek

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