[PATCH] Fix atomic_full_barrier on x86 and x86_64.

[Torvald Riegel]

On Wed, 2014-10-29 at 22:54 +0000, Joseph S. Myers wrote:
> On Wed, 29 Oct 2014, Torvald Riegel wrote:
> 
> > So, mfence seems to have been introduced with SSE2.  Should I try to
> > test for SSE2 specifically, or rather assume SSE2 support for i786?
> 
> I think the i786 directories should be removed; config.guess will never 
> return such a processor name for GNU/Linux at least (I don't know what it 
> returns on Hurd).  The comment in sysdeps/i386/i786/Implies suggests it 
> was for PII, but PII was still family 6 (and family 15 came after family 
> 6, I don't think there were any x86 processors with family numbers 7 to 
> 14).
> 
> So, anything conditional on SSE2 should test for __SSE2__.

How does this updated patch look?  The non-SSE full barrier is what,
AFAIU, GCC emits.

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