Simplify.hs depends on typechecker

[Joachim Breitner]

Hi,

while rebuilding Simplify.o only I noticed that all of the type
checker, and HsSyn stuff, and renamer stuff, and so needed to be
rebuilt, which I found strange.

After a little investigation, it seems that the simplifier depends on
CoreMonad, and that pulls some very few type-checker related things:

1.
    import TcRnMonad        ( initTcForLookup )
    import {-# SOURCE #-} TcSplice ( lookupThName_maybe )

for 

    thNameToGhcName :: TH.Name -> CoreM (Maybe Name)
    thNameToGhcName th_name = do
        hsc_env <- getHscEnv
        liftIO $ initTcForLookup hsc_env (lookupThName_maybe th_name)

which is not even used in GHC, but only in GHC Plugins, so this could
probably be moved to a separate module pulled in by GhcPlugins.hs

2.

    import TcEnv            ( lookupGlobal )

for

    instance MonadThings CoreM where
        lookupThing name = do { hsc_env <- getHscEnv
                              ; liftIO $ lookupGlobal hsc_env name }

This might be a bit harder to disentangle. But if successful, it would
probably make building GHC in parallel quite a bit faster. And it just
seems strange to me that the Core-to-Core code should depend on the
type checker…


I’m sending this out there in case someone has dug in that direction
before and has insights to share.


Greetings,
Joachim

(Attached is a transitively reduced dependency graph of Simplify.hs,
created using Iavor’s https://github.com/yav/graphmod/wiki).


-- 
Joachim “nomeata” Breitner
  mail at joachim-breitner.de
  https://www.joachim-breitner.de/
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