Re: fast softint support for sparc64

[Eduardo Horvath <eeh%NetBSD.org@localhost>]

On Sat, 18 Jun 2011, David Laight wrote:

> On Sat, Jun 18, 2011 at 05:14:38AM +0900, Takeshi Nakayama wrote:
> > >>> Eduardo Horvath <eeh%NetBSD.org@localhost> wrote
> > 
> > > If you're trying to order the store to the CI_MTX_COUNT with the store to 
> > > L_CTXSWTCH then I think it should be #StoreStore.  
> > > 
> > > Note the comment in membar_ops.S:
> > > 
> > > /* These assume Total Store Order (TSO) */
> > > 
> > > Um, if you're running TSO then you don't need any membars at all.  We 
> > > should really be coding this for RMO to get some performance 
> > > improvements.  
> > > Otherwise leaving them out will reduce instruction count and CPU cycles.
> > 
> > Ok, I will just leave it out.  Thank you for detailed comment.
> 
> Even assuming TSO, some of this code might require that the compiler not
> re-order reads/writes (ie have memory locations cached in registers).

Yeah, but we're talking about assemply code here.  And even when I look at 
the C version the location of the membar call doesn't really make much 
sense to me.

Eduardo