David Daney wrote:
There is nothing that says that __sync_compar_and_swap() cannot expand to a libcall.
Ideally a GCC user would not have to write target specific assembly for this.
If I just had one algorithm for my locking problem then, yes, that would be fine. But as it happens I have two algorithms, one of which uses atomic compare-and-set and one of which uses atomic swap. I want to use whichever maps best to the target architecture. So I need to be able to distinguish between a builtin that expands to a couple of inline instructions and a builtin that expands to a library call.
If someone would like to add OS-specific builtins for the other atomic operations, that's fine, but please do something so that I can identify that they involve library or kernel calls (e.g. #define __SYNC_COMPARE_AND_SET_n=ASM vs. #define __SYNC_COMPARE_AND_SET_n=LIBRARY.) But that looks like a lot more work than just adding one builtin for SWP, which is all that I need.
Phil.
