[WARP] Convergence tests failure

[luciechoi]

Convergence tests are failing on Warp.

Created a separate issue for Clang

[s-perron]

Hello Sarah,

We don't know where the open an issue for wrap. Can you bring this to the attention of the right people? Thanks.

[spall]

Hello Sarah,

We don't know where the open an issue for wrap. Can you bring this to the attention of the right people? Thanks.

Could you or @luciechoi summarize the issue you are seeing with warp, so I can send it along to the right people? Thanks.

[s-perron]

We just added at test that fails when compiled with DXC and run on WARP. I'm guessing the issue is not DXC (it pass on Intel when compiled with DXC). I'll leave that for you to decided how much you want to look at code generated by DXC before passing it off to WARP.

https://github.com/llvm/offload-test-suite/blob/e939efa266beb592a592c1a4504ce87eb0d3936b/test/Feature/MaximalReconvergence/subgroup_uniform_control_flow.test

[spall]

I've followed up with the warp team and it doesn't look like this is a bug. Warp appears to have run the shader with wave size 4 instead of the assumed 8, leading to the result you saw. I confirmed this is the case by setting the Wave Size to 8 and the test then passes.

I think the fix here is to update the test to not be fragile to wave size or to set the wave size to 8, but setting the wave size doesn't seem to be supported by all offload test suite hardware; I had to use sm 6.8 but some hardware doesn't seem to accept above sm6.5.

[s-perron]

@spall Sorry about that. I didn't think about the wave size changing.

@luciechoi Can you look at the tests and try to update them? We can discuss it privately.