[llvm] [TableGen] Add a field to filter out GenericTable entries (PR #65458)

[Wang Pengcheng via llvm-commits]

wangpc-pp wrote:

> The change looks OK to me, but this should surely have a test in `llvm/test/TableGen`.

Thanks! I was planning to add a test but I can't find existed tests for `GenericTable`. I will try to add one later.
> 
> You don't say what the use case for this is. I'm guessing it might be so you can construct two `GenericTable`s with the same `FilterClass`, so that they select from the same overall set of records, but assign them different `FilterClassField` values so that they include different subsets of the records of that class?

Yes! This can be a scenario! And I posted another PR #65460 to show the usage.
> 
> Perhaps demonstrating that in the new test would be a good idea, and maybe mentioning it in the documentation too. (Documentation is at least as much for "what feature can I use to do this thing?" as "what does this feature do?")\

Will do, thanks!



https://github.com/llvm/llvm-project/pull/65458