[llvm] [RFC][TableGen] Restructure TableGen Source (PR #80847)

[NAKAMURA Takumi via llvm-commits]

https://github.com/chapuni commented:

Excuse me, it will take longer time for me to review. I am dubious a bit to this direction.

Re. formatting changes, It's good thing to reformat files to be moved. Then I suggest you to split reformatting commits in advance before merging this.

https://github.com/llvm/llvm-project/pull/80847