[reenable known-case after return optimization for Grin.
John Meacham <john@repetae.net>**20070606123308] hunk ./Grin/Simplify.hs 344
-        {-
-    f (Return n :>>= b :-> Case b' as :>>= lr) | isKnown n, b == [b'] = do
+    f (Return [n] :>>= b :-> Case b' as :>>= lr) | isKnown n, b == [b'] = do
hunk ./Grin/Simplify.hs 347
-        return (Return n :>>= b :-> r)
-    f (Return n :>>= b :-> Case b' as ) | isKnown n, b == [b'] = do
+        return (Return [n] :>>= b :-> r)
+    f (Return [n] :>>= b :-> Case b' as ) | isKnown n, b == [b'] = do
hunk ./Grin/Simplify.hs 351
-        return (Return n :>>= b :-> r)
+        return (Return [n] :>>= b :-> r)
+        {-
hunk ./Grin/Simplify.hs 445
---            UnboxTag -> do
---                mtick "Optimize.optimize.let-unbox-tag"
---                let (va:_vr) = [ v | v <- [v1..], not $ v `Set.member` fv ]
---                return ((combine postEval TyTag cs :>>= Var va TyTag :-> Return (NodeV va [])) :>>= lr)