[Bug target/39677] AMD Opteron E needs workaround for lock erratum

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=39677

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |INVALID

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So reading https://www.amd.com/system/files/TechDocs/25759.pdf and errata #147,
the errata only occurs if lock is not there:
The erratum will not occur if there is a LOCK prefix on the read-modify-write
instruction. 

And GCC never emits a cmpxchg without a lock prefix so there is nothing to be
done.