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

[Jocelyn Mayer]

On Wed, 2007-09-19 at 12:56 +0200, Alexander Graf wrote:
> On Sep 19, 2007, at 1:28 AM, Paul Brook wrote:
> 
> >>>> Ok, I will try to shift the intercepts in an uint_64 flags variable
> >>>> in the TB.
> >>
> >> 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.
> >
> > Paul
> 
> here comes the patch.

The patch looks correct to me, I'm just wondering why a cast to 32 bits
is needed in mips code ?

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.