[llvm] [TableGen] fix tlbgen for EncodingByHwMode (PR #84906)

[Jason Eckhardt via llvm-commits]

nvjle wrote:

> Hi [nvjle](https://github.com/nvjle), [kparzysz](https://github.com/kparzysz). I might take a few days to organize my patch and perform some more in-depth checks (such as enabling the EncodingByHwMode functionality on other backends like RISCV, and build tablegen in debug mode to dump some records) to ensure the functionality is correct, although we have already conducted numerous CI tests on this patch in our local project. I will try to decouple the code of 'DecoderEmitter' part within one or two days to submit a pull request first. Thank you very much for your patient review and valuable comments.

Sounds good @superZWT123, and doing the `DecoderEmitter` part first makes sense. From your paragraph earlier, you essentially want a less aggressive suppression compared to what exists in TOT today. That suggests changing the existing boolean suppress option to an integer option which has two modes, e.g. 0 for existing suppression, and 1 for less aggressive suppression (being an obscure option of TableGen, a simple integer option is fine). That preserves the existing code and functionality while also adding the less aggressive form. Also, with respect to removing the existing `AllModes` suffix of the current suppression, I have no objection. 



https://github.com/llvm/llvm-project/pull/84906