1. Improve pipline's comment
2. Decompose insert_slice_async when load vector size is not supported
3. Add a test that could fail our gemm code
Copy my comments here:
There's a knob that may cause performance regression when decomposition
has been performed. We should remove this knob once we have thorough
analysis on async wait. Currently, we decompose `insert_slice_async`
into `load` and `insert_slice` without knowing which `async_wait` is
responsible for the `insert_slice_async`. To guarantee correctness, we
blindly set the `async_wait` to wait for all async ops if any `insert_slice_async` has been decomposed.
There are two options to improve this:
1. We can perform a dataflow analysis to find the `async_wait` that is
responsible for the `insert_slice_async` in the backend.
4. We can modify the pipeline to perform the decomposition before the
`async_wait` is inserted. However, it is also risky because we don't
know the correct vectorized shape yet in the pipeline pass. Making the
pipeline pass aware of the vectorization could introduce additional
dependencies on the AxisInfoAnalysis and the Coalesce analysis.