Re: [RFC/PATCH] Make powerpc64 use __thread for per-cpu variables

[Segher Boessenkool]

> > > How do you plan to address the compiler optimizing
> >  ...
> > > Across the schedule, we may have changed cpus, making the cached
> > > address invalid.
> >
> > Per-cpu variables need to be accessed only with preemption
> > disabled.  And the preemption enable/disable operations
> > provide a compiler memory barrier.
>
> No, Richard has a point, it's not the value that is the concern, it's
> the address, which gcc could assume is still valid after a barrier.
> Drat.

Would an asm clobber of GPR13 in the schedule routines (or a wrapper
for them, or whatever) work?


Segher

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