[Relay] [Bugfix] Fix some bugs of dominator pattern

[kfeng123]

This PR solves Issue 1 and Issue 2 of dominator pattern as described in the pre-RFC

[tvm-bot]

Thanks for contributing to TVM! Please refer to the contributing guidelines https://tvm.apache.org/docs/contribute/ for useful information and tips. Please request code reviews from Reviewers by @-ing them in a comment.

• cc @shingjan _{See #10317 for details}

_{Generated by tvm-bot}

[tqchen]

cc @ganler @masahi @yelite would be good if you can help review. @kfeng123 can you also send a PR to unity and update dominator pattern in https://github.com/apache/tvm/blob/unity/include/tvm/relax/dataflow_pattern.h Thank you!

[ganler]

cc @ganler @masahi @yelite would be good if you can help review. @kfeng123 can you also send a PR to unity and update dominator pattern in https://github.com/apache/tvm/blob/unity/include/tvm/relax/dataflow_pattern.h Thank you!

Note that Relax pattern language does not syntactically model topological patterns such as the dominator pattern, but instead dependency constraints need to be specified to model such patterns.

I need to take a while to follow up the pre-RFC for better understanding the intent of this PR but feel free to go ahead merging it without me. :)

[kfeng123]

I am not familiar with the unity branch. I would like to learn the pattern matching design there and contribute to it. But it may take some time.