+\begin{code}
+emptyFVInfo :: FreeVarsInfo
+emptyFVInfo = emptyVarEnv
+
+singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
+singletonFVInfo id ImportBound info
+ | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, TopLevelHasCafs, info)
+ | otherwise = emptyVarEnv
+singletonFVInfo id (LetBound top_level _ _) info
+ = unitVarEnv id (id, top_level, info)
+singletonFVInfo id other info
+ = unitVarEnv id (id, NotTopLevelBound, info)
+
+tyvarFVInfo :: TyVarSet -> FreeVarsInfo
+tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
+ where
+ add tv fvs = extendVarEnv fvs tv (tv, NotTopLevelBound, noBinderInfo)
+
+unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
+unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
+
+unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
+unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
+
+minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo
+minusFVBinders vs fv = foldr minusFVBinder fv vs
+
+minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo
+minusFVBinder v fv | isId v && opt_KeepStgTypes
+ = (fv `delVarEnv` v) `unionFVInfo`
+ tyvarFVInfo (tyVarsOfType (idType v))
+ | otherwise = fv `delVarEnv` v
+ -- When removing a binder, remember to add its type variables
+ -- c.f. CoreFVs.delBinderFV
+
+elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
+elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
+
+lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
+-- Find how the given Id is used.
+-- Externally visible things may be used any old how
+lookupFVInfo fvs id
+ | isExternallyVisibleName (idName id) = noBinderInfo
+ | otherwise = case lookupVarEnv fvs id of
+ Nothing -> noBinderInfo
+ Just (_,_,info) -> info
+
+allFVs :: FreeVarsInfo -> [Id] -- Non-top-level things only
+allFVs fvs = [id | (id,_,_) <- rngVarEnv fvs]
+
+getFVs :: FreeVarsInfo -> [Id] -- Non-top-level things only
+getFVs fvs = [id | (id,NotTopLevelBound,_) <- rngVarEnv fvs]
+
+getFVSet :: FreeVarsInfo -> IdSet
+getFVSet fvs = mkVarSet (getFVs fvs)
+
+plusFVInfo (id1,top1,info1) (id2,top2,info2)
+ = ASSERT (id1 == id2 && top1 == top2)
+ (id1, top1, combineStgBinderInfo info1 info2)
+\end{code}