import TysPrim ( realWorldStatePrimTy )
import UniqFM ( plusUFM_C, addToUFM_Directly, lookupUFM_Directly,
keysUFM, minusUFM, ufmToList, filterUFM )
-import Type ( isUnLiftedType, coreEqType )
+import Type ( isUnLiftedType, coreEqType, splitTyConApp_maybe )
+import Coercion ( coercionKind )
import CoreLint ( showPass, endPass )
import Util ( mapAndUnzip, mapAccumL, mapAccumR, lengthIs )
import BasicTypes ( Arity, TopLevelFlag(..), isTopLevel, isNeverActive,
dmdAnal sigs dmd (Var var)
= (dmdTransform sigs var dmd, Var var)
+dmdAnal sigs dmd (Cast e co)
+ = (dmd_ty, Cast e' co)
+ where
+ (dmd_ty, e') = dmdAnal sigs dmd' e
+ to_co = snd (coercionKind co)
+ dmd'
+ | Just (tc, args) <- splitTyConApp_maybe to_co
+ , isRecursiveTyCon tc = evalDmd
+ | otherwise = dmd
+ -- This coerce usually arises from a recursive
+ -- newtype, and we don't want to look inside them
+ -- for exactly the same reason that we don't look
+ -- inside recursive products -- we might not reach
+ -- a fixpoint. So revert to a vanilla Eval demand
+
dmdAnal sigs dmd (Note n e)
= (dmd_ty, Note n e')
where
- (dmd_ty, e') = dmdAnal sigs dmd' e
- dmd' = case n of
- Coerce _ _ -> evalDmd -- This coerce usually arises from a recursive
- other -> dmd -- newtype, and we don't want to look inside them
- -- for exactly the same reason that we don't look
- -- inside recursive products -- we might not reach
- -- a fixpoint. So revert to a vanilla Eval demand
+ (dmd_ty, e') = dmdAnal sigs dmd e
dmdAnal sigs dmd (App fun (Type ty))
= (fun_ty, App fun' (Type ty))
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If the rhs is a thunk, we usually forget the CPR info, because
it is presumably shared (else it would have been inlined, and
-so we'd lose sharing if w/w'd it into a function.
+so we'd lose sharing if w/w'd it into a function). E.g.
+
+ let r = case expensive of
+ (a,b) -> (b,a)
+ in ...
+
+If we marked r as having the CPR property, then we'd w/w into
+
+ let $wr = \() -> case expensive of
+ (a,b) -> (# b, a #)
+ r = case $wr () of
+ (# b,a #) -> (b,a)
+ in ...
+
+But now r is a thunk, which won't be inlined, so we are no further ahead.
+
However, if the strictness analyser has figured out (in a previous
iteration) that it's strict, then we DON'T need to forget the CPR info.