Re: CVS commit: src/sys/arch/sparc

[Alan Barrett <apb%cequrux.com@localhost>]

On Sat, 19 Oct 2013, matthew green wrote:
> Module Name:    src
> Committed By:   mrg
> Date:           Sat Oct 19 19:40:23 UTC 2013
>
> Modified Files:
>         src/sys/arch/sparc/dev: if_ie_obio.c kd.c tctrl.c ts102.c
>         src/sys/arch/sparc/include: pmap.h
>         src/sys/arch/sparc/sparc: cpuvar.h memecc.c timer.c
>
> Log Message:
> - remove unused but set variables.
> - use __USE() where necessary.
> - remove useless 'volatile' markers

I am not sure that those volatile markers are useless.

For example:

> #define raise_ipi(cpi,lvl)      do {                    \
> -       volatile int x;                                 \
> +       int x;                                          \
>         (cpi)->intreg_4m->pi_set = PINTR_SINTRLEV(lvl);   \
> -       x = (cpi)->intreg_4m->pi_pend;                    \
> +       x = (cpi)->intreg_4m->pi_pend; __USE(x);  \
> } while (0)

I think that the change from the use of volatile to the use of 
__USE() is a change from reliance on the C standard's guarantee 
that the memory location behind (cpi)->intreg_4m->pi_pend really 
will be accessed, to a reliance on what a particular compiler 
happens to do in this situation.

--apb (Alan Barrett)