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So; on a 64 bit SPARC CPU which is v9 compliant, there exists I know a cas instruction. This operates on single word length values.
I’ve also seen on the web reference to a casx instruction – but I can’t find out anything much more about it.
I’m wondering – is this a double word compare and swap?
And if not, the general question is; IS there a double word compare and swap?
Sparc64 – alone amongst modern CPUs – implements neither double wide CAS nor LL/SC. As such, implementing lock-free code is problematic. There a solutions, but they are solutions to a problem (ABA) which does not exist on other platforms because of their support for CAS or LL/SC. Furthermore, a range of lock-free algorithms cannot be implemented on Sparce because of this limitation.