Glenn Schrader wrote:
The cas instruction is supported on the sparc v8plus and v9. Support for just sparc v8 is inadequate. In that case you need to use the swap instruction and some looping to do something similar to a cas. Another wrinkle is that just removing the defined(__sparcv8) from the above condition doesn't quite do the right thing with gcc. From what I can tell gcc is setting __sparcv8 even if -mcpu=v9 is specified. I have a v9 processor but I'm running 32 bit solaris so could gcc be basing the __sparcv8/v9 defines on the OS rather than the cpu type? The biggest difference between the v8 and v9 cpus is 64bit support.
The problem is that some versions of GCC are setting the v9 macro only in 64-bit builds (probably because of existing code that makes this assumption) and I'm not sure what we can do about that. Is __sparcv8plus defined for you? It's the right macro in principle, but I suspect that it's not being used because it doesn't work.