+\begin{code}
+hasCafRefs :: IdEnv HowBound -> CoreExpr -> CafInfo
+-- Only called for the RHS of top-level lets
+hasCafRefss :: IdEnv HowBound -> [CoreExpr] -> CafInfo
+ -- predicate returns True for a given Id if we look at this Id when
+ -- calculating the result. Used to *avoid* looking at the CafInfo
+ -- field for an Id that is part of the current recursive group.
+
+hasCafRefs p expr
+ | isCAF expr || isFastTrue (cafRefs p expr) = MayHaveCafRefs
+ | otherwise = NoCafRefs
+
+ -- used for recursive groups. The whole group is set to
+ -- "MayHaveCafRefs" if at least one of the group is a CAF or
+ -- refers to any CAFs.
+hasCafRefss p exprs
+ | any isCAF exprs || isFastTrue (cafRefss p exprs) = MayHaveCafRefs
+ | otherwise = NoCafRefs
+
+-- cafRefs compiles to beautiful code :)
+
+cafRefs p (Var id)
+ | isLocalId id = fastBool False
+ | otherwise =
+ case lookupVarEnv p id of
+ Just (LetBound TopLevelHasCafs _ _) -> fastBool True
+ Just (LetBound _ _ _) -> fastBool False
+ Nothing -> fastBool (cgMayHaveCafRefs (idCgInfo id)) -- imported Ids
+
+cafRefs p (Lit l) = fastBool False
+cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
+cafRefs p (Lam x e) = cafRefs p e
+cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
+cafRefs p (Case e bndr alts) = fastOr (cafRefs p e)
+ (cafRefss p) (rhssOfAlts alts)
+cafRefs p (Note n e) = cafRefs p e
+cafRefs p (Type t) = fastBool False
+
+cafRefss p [] = fastBool False
+cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
+
+-- hack for lazy-or over FastBool.
+fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))
+
+isCAF :: CoreExpr -> Bool
+-- Only called for the RHS of top-level lets
+isCAF e = not (rhsIsNonUpd e)
+ {- ToDo: check type for onceness, i.e. non-updatable thunks? -}
+
+
+rhsIsNonUpd :: CoreExpr -> Bool
+ -- True => Value-lambda, constructor, PAP
+ -- This is a bit like CoreUtils.exprIsValue, with the following differences:
+ -- a) scc "foo" (\x -> ...) is updatable (so we catch the right SCC)
+ --
+ -- b) (C x xs), where C is a contructors is updatable if the application is
+ -- dynamic: see isDynConApp
+ --
+ -- c) don't look through unfolding of f in (f x). I'm suspicious of this one
+
+-- This function has to line up with what the update flag
+-- for the StgRhs gets set to in mkStgRhs (above)
+--
+-- When opt_RuntimeTypes is on, we keep type lambdas and treat
+-- them as making the RHS re-entrant (non-updatable).
+rhsIsNonUpd (Lam b e) = isRuntimeVar b || rhsIsNonUpd e
+rhsIsNonUpd (Note (SCC _) e) = False
+rhsIsNonUpd (Note _ e) = rhsIsNonUpd e
+rhsIsNonUpd other_expr
+ = go other_expr 0 []
+ where
+ go (Var f) n_args args = idAppIsNonUpd f n_args args
+
+ go (App f a) n_args args
+ | isTypeArg a = go f n_args args
+ | otherwise = go f (n_args + 1) (a:args)
+
+ go (Note (SCC _) f) n_args args = False
+ go (Note _ f) n_args args = go f n_args args
+
+ go other n_args args = False
+
+idAppIsNonUpd :: Id -> Int -> [CoreExpr] -> Bool
+idAppIsNonUpd id n_val_args args
+ | Just con <- isDataConId_maybe id = not (isCrossDllConApp con args)
+ | otherwise = n_val_args < idArity id
+
+isCrossDllConApp :: DataCon -> [CoreExpr] -> Bool
+isCrossDllConApp con args = isDllName (dataConName con) || any isCrossDllArg args
+-- Top-level constructor applications can usually be allocated
+-- statically, but they can't if
+-- a) the constructor, or any of the arguments, come from another DLL
+-- b) any of the arguments are LitLits
+-- (because we can't refer to static labels in other DLLs).
+-- If this happens we simply make the RHS into an updatable thunk,
+-- and 'exectute' it rather than allocating it statically.
+-- All this should match the decision in (see CoreToStg.coreToStgRhs)
+
+
+isCrossDllArg :: CoreExpr -> Bool
+-- True if somewhere in the expression there's a cross-DLL reference
+isCrossDllArg (Type _) = False
+isCrossDllArg (Var v) = isDllName (idName v)
+isCrossDllArg (Note _ e) = isCrossDllArg e
+isCrossDllArg (Lit lit) = isLitLitLit lit
+isCrossDllArg (App e1 e2) = isCrossDllArg e1 || isCrossDllArg e2 -- must be a type app
+isCrossDllArg (Lam v e) = isCrossDllArg e -- must be a type lam