-modifyInlinePragma id fn = modifyIdInfo id (\info -> setInlinePragInfo (fn (inlinePragInfo info)) info)
-
-idWantsToBeINLINEd :: Id -> Bool
-idWantsToBeINLINEd id = case getInlinePragma id of
- IWantToBeINLINEd -> True
- IMustBeINLINEd -> True
- other -> False
-
-idMustNotBeINLINEd id = case getInlinePragma id of
- IMustNotBeINLINEd -> True
- IAmASpecPragmaId -> True
- IAmALoopBreaker -> True
- other -> False
-
-idMustBeINLINEd id = case getInlinePragma id of
- IMustBeINLINEd -> True
- other -> False
-
-isSpecPragmaId id = case getInlinePragma id of
- IAmASpecPragmaId -> True
- other -> False
+modifyInlinePragma id fn = modifyIdInfo (\info -> info `setInlinePragInfo` (fn (inlinePragInfo info))) id
+\end{code}
+
+
+ ---------------------------------
+ -- ONE-SHOT LAMBDAS
+\begin{code}
+idLBVarInfo :: Id -> LBVarInfo
+idLBVarInfo id = lbvarInfo (idInfo id)
+
+isOneShotBndr :: Id -> Bool
+-- This one is the "business end", called externally.
+-- Its main purpose is to encapsulate the Horrible State Hack
+isOneShotBndr id = isOneShotLambda id || (isStateHackType (idType id))
+
+isStateHackType :: Type -> Bool
+isStateHackType ty
+ | opt_NoStateHack
+ = False
+ | otherwise
+ = case splitTyConApp_maybe ty of
+ Just (tycon,_) -> tycon == statePrimTyCon
+ other -> False
+ -- This is a gross hack. It claims that
+ -- every function over realWorldStatePrimTy is a one-shot
+ -- function. This is pretty true in practice, and makes a big
+ -- difference. For example, consider
+ -- a `thenST` \ r -> ...E...
+ -- The early full laziness pass, if it doesn't know that r is one-shot
+ -- will pull out E (let's say it doesn't mention r) to give
+ -- let lvl = E in a `thenST` \ r -> ...lvl...
+ -- When `thenST` gets inlined, we end up with
+ -- let lvl = E in \s -> case a s of (r, s') -> ...lvl...
+ -- and we don't re-inline E.
+ --
+ -- It would be better to spot that r was one-shot to start with, but
+ -- I don't want to rely on that.
+ --
+ -- Another good example is in fill_in in PrelPack.lhs. We should be able to
+ -- spot that fill_in has arity 2 (and when Keith is done, we will) but we can't yet.
+
+
+-- The OneShotLambda functions simply fiddle with the IdInfo flag
+isOneShotLambda :: Id -> Bool
+isOneShotLambda id = case idLBVarInfo id of
+ IsOneShotLambda -> True
+ NoLBVarInfo -> False
+
+setOneShotLambda :: Id -> Id
+setOneShotLambda id = modifyIdInfo (`setLBVarInfo` IsOneShotLambda) id
+
+clearOneShotLambda :: Id -> Id
+clearOneShotLambda id
+ | isOneShotLambda id = modifyIdInfo (`setLBVarInfo` NoLBVarInfo) id
+ | otherwise = id
+
+-- But watch out: this may change the type of something else
+-- f = \x -> e
+-- If we change the one-shot-ness of x, f's type changes