Depends on D131228
In GCC they apparently used dbar 0x700 for open-coded atomic CAS templates, that seemed to result from a hardware erratum. If in a future hardware iteration this dbar is going to become unnecessary, coding dbar 0x700 here might be a good idea.
You may confirm with the CPU designers and the GCC team for this.
Have to rebase...
Thank you for your reminder. After confirmation, Dbar 0x700 will be used in the subsequent CAS operation, and Dbar 0 is sufficient in the current atomic binary operation.