-occAnalTop :: OccEnv -- What's in scope
- -> [CoreBinding]
- -> (IdEnv BinderInfo, -- Occurrence info
- IdEnv Id, -- Indirection elimination info
- [SimplifiableCoreBinding]
- )
-
-occAnalTop env [] = (emptyDetails, nullIdEnv, [])
-
--- Special case for eliminating indirections
-occAnalTop env (NonRec exported_id (Var local_id) : binds)
- | isExported exported_id && -- Only if this is exported
-
- isLocallyDefined local_id && -- Only if this one is defined in this
- -- module, so that we *can* change its
- -- binding to be the exported thing!
-
- not (isExported local_id) && -- Only if this one is not itself exported,
- -- since the transformation will nuke it
-
- not (omitIfaceSigForId local_id) && -- Don't do the transformation if rhs_id is
- -- something like a constructor, whose
- -- definition is implicitly exported and
- -- which must not vanish.
- -- To illustrate the preceding check consider
- -- data T = MkT Int
- -- mkT = MkT
- -- f x = MkT (x+1)
- -- Here, we'll make a local, non-exported, defn for MkT, and without the
- -- above condition we'll transform it to:
- -- mkT = \x. MkT [x]
- -- f = \y. mkT (y+1)
- -- This is bad because mkT will get the IdDetails of MkT, and won't
- -- be exported. Also the code generator won't make a definition for
- -- the MkT constructor.
- -- Slightly gruesome, this.
-
-
- not (maybeToBool (lookupIdEnv ind_env local_id))
- -- Only if not already substituted for
-
- = -- Aha! An indirection; let's eliminate it!
- (scope_usage, ind_env', binds')
- where
- (scope_usage, ind_env, binds') = occAnalTop env binds
- ind_env' = addOneToIdEnv ind_env local_id exported_id