(In reply to Vedran Miletić from comment #5)
> Can you dig the patch somewhere? I have a Caicos at hand and I would really
> like to test atomic compare-and-swap.

you can try my github branch [0], you'll need the last 5 patches (2-3 can be
skipped since it's just revert).
but I rebase a lot so things might brake.

It passes noret piglit tests, and _noret should work OK, _return variants will
give LLVM ERROR: Cannot select.
uncommenting the FIXME parts enables return variants, but it will brake for
more than one WI as every WI uses address 0 as scratchpad.

Jan

[0] https://github.com/jvesely/llvm