[Bug target/68945] enable libcilkrts on SPARC

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68945

--- Comment #11 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> * In runtime/config/sparc/os-unix-sysdep.c (__cilkrts_getticks) I needed
> different
>   32- and 64-bit versions.  I tested the result in standalone program which
> just
>   printed the result.

This looks good to me.

> * One thing I wonder about is runtime/config/sparc/os-fence.h: when using
>   __sync_synchronize, gcc emits membar #StoreLoad, while Stefan's patch had
>   membar    #LoadLoad | #LoadStore | #StoreStore | #StoreLoad.  It seems that
>   all but #StoreLoad are no-ops for TSO SPARC CPUs, but I'd better get this
> right.

__sync_synchronize emits the minimum memory barrier for the memory model, which
is TSO on Solaris so only #StoreLoad is needed.  The 4 flags are needed for RMO
theoretically, but I'm not sure RMO ever existed in real life.