Does it sound a good idea to implement "backend plugins"?

[Shao, Cheng]

Hi all,

I'm thinking of adding "backend plugins" in the current Plugins
mechanism which allows one to inspect/modify the IRs post simplifier
pass (STG/Cmm), similar to the recently added source plugins for HsSyn
IRs. This can be useful for anyone creating a custom GHC backend to
target an experimental platform (e.g. the Asterius compiler which
targets WebAssembly), and previously in order to retrieve those IRs
from the regular pipeline, we need to use Hooks which is somewhat
hacky.

Does this sound a good idea to you? If so, I can open a trac ticket
and a Phab diff for this feature.

Best,
Shao Cheng