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Re: [RFC] Fix full memory barrier on SPARC-V8
From: Eric Botcazou <ebotcazou@adacore.com>
Date: Tue, 28 Jun 2011 23:27:43 +0200
> With the pristine compiler, the test passes with -mcpu=v9 but fails otherwise.
> It passes with the patched compiler. However, I suspect that we would still
> have problems with newer UltraSparc CPUs supporting full RMO, because the new
> insn membar_v8 is only half a memory barrier for V9.
Linux doesn't ever run the cpu in the RMO memory model any more. All
sparc64 chips run only in TSO now.
All of the Niagara chips implement an even stricter than TSO memory
model, and the membars we used to have all over the kernel to handle
that properly were just wasted I-cache space. So I just moved
unilaterally to TSO everywhere and killed off the membars necessitated
by RMO.