Re: [Fwd: Re: [Qemu-devel] [PATCH] SVM support]

[Paul Brook]

> > >> OK, great. Having 64 bits may also help for additional (ie future...)
> > >> features in PowerPC 64 emulation.
> > >
> > > Maybe worth letting the target say whether it needs 32 or 64-bit
> > > flags.
> > > The flag lookup is likely to be on a hot path.
> > >
>
> I may be wrong, but it seems to me that TB flags are only used to be
> compared in tb_find_fast and tb_find_slow, which are not a very fast
> path (we come here when we cannot jump directly to the next tb and are
> not in the most time critical code) then we can afford adding a few asm
> instructions (I would say max 2 ?) to replace a 32 bits comparison with
> a 64 bits one. My feeling is that the performance loss here won't be
> sensible, but that may need to be proved.

For some reason I thought the flags were also used in the hash lookup. This is 
not the case, so I withdraw my objection.

Paul