Re: [AD] option to allow SSE instructions

[AJ <aj@xxxxxxxxxx>]

Peter Wang wrote:
> On 2009-03-16, AJ <aj@xxxxxxxxxx> wrote:
>   
> > Does this mean we can use  InterlockedXX()s also ?
> > They'd make things like the threading easier to manage, and reduce that 
> > hideous critical section locking (all for a read/write to bool ...  talk 
> > about overhead!!!)
> >     
>
> Which critical section are you thinking of?
>   


_al_thread_should_stop

in

/4.9/include/allegro5/platform/aintwthr.h


I presume this function gets called in a while loop, the user waiting 
for its state to change.
too tight a loop, and it'll chew cpu.
that is why things like the  cpu  pause instruction was invented.



> You can use InterlockedXX if it makes sense (at least some atomic ops
> were already possible on late 486s).  Generally I think it's not
> worthwhile; it's much harder to get right than using mutexes/critical
> sections.
>   


when the only thing your protecting is a single var,  the overhead of 
critical sections is ..er.. overkill.

when there are multiple vars, critical sections are easier to 'get right'.

however, this code is simply protecting a bool state flag.