-- Perform this transform everywhere
castsimpltop = everywhere ("castsimpl", castsimpl)
+
+--------------------------------
+-- Lambda simplication
+--------------------------------
+-- Ensure that a lambda always evaluates to a let expressions or a simple
+-- variable reference.
+lambdasimpl, lambdasimpltop :: Transform
+-- Don't simplify a lambda that evaluates to let, since this is already
+-- normal form (and would cause infinite loops).
+lambdasimpl expr@(Lam _ (Let _ _)) = return expr
+-- Put the of a lambda in its own binding, but not when the expression is
+-- already a local variable, or not representable (to prevent loops with
+-- inlinenonrep).
+lambdasimpl expr@(Lam bndr res) = do
+ repr <- isRepr res
+ local_var <- Trans.lift $ is_local_var res
+ if not local_var && repr
+ then do
+ id <- Trans.lift $ mkBinderFor res "res"
+ change $ Lam bndr (Let (NonRec id res) (Var id))
+ else
+ -- If the result is already a local var or not representable, don't
+ -- extract it.
+ return expr
+
+-- Leave all other expressions unchanged
+lambdasimpl expr = return expr
+-- Perform this transform everywhere
+lambdasimpltop = everywhere ("lambdasimpl", lambdasimpl)
+
--------------------------------
-- let derecursification
--------------------------------
-- Nothing is liftable, just return
[] -> return expr
-- Something can be lifted, generate a new let expression
- _ -> change $ MkCore.mkCoreLets newbinds res
+ _ -> change $ mkNonRecLets liftable (Let (Rec nonliftable) res)
where
-- Make a list of all the binders bound in this recursive let
bndrs = map fst binds
-- See which bindings are liftable
(liftable, nonliftable) = List.partition canlift binds
- -- Create nonrec bindings for each liftable binding and a single recursive
- -- binding for all others
- newbinds = (map (uncurry NonRec) liftable) ++ [Rec nonliftable]
-- Any expression that does not use any of the binders in this recursive let
-- can be lifted into a nonrec let. It can't use its own binder either,
-- since that would mean the binding is self-recursive and should be in a
-- Perform this transform everywhere
letflattop = everywhere ("letflat", letflat)
+--------------------------------
+-- empty let removal
+--------------------------------
+-- Remove empty (recursive) lets
+letremove, letremovetop :: Transform
+letremove (Let (Rec []) res) = change $ res
+-- Leave all other expressions unchanged
+letremove expr = return expr
+-- Perform this transform everywhere
+letremovetop = everywhere ("letremove", letremove)
+
--------------------------------
-- Simple let binding removal
--------------------------------
-- Unused let binding removal
--------------------------------
letremoveunused, letremoveunusedtop :: Transform
-letremoveunused expr@(Let (Rec binds) res) = do
+letremoveunused expr@(Let _ _) = do
-- Filter out all unused binds.
let binds' = filter dobind binds
-- Only set the changed flag if binds got removed
- changeif (length binds' /= length binds) (Let (Rec binds') res)
+ changeif (length binds' /= length binds) (mkNonRecLets binds' res)
where
+ (binds, res) = flattenLets expr
bound_exprs = map snd binds
-- For each bind check if the bind is used by res or any of the bound
-- expressions
-- TODO: We would very much like to use GHC's CSE module for this, but that
-- doesn't track if something changed or not, so we can't use it properly.
letmerge, letmergetop :: Transform
-letmerge expr@(Let (Rec binds) res) = do
+letmerge expr@(Let _ _) = do
+ let (binds, res) = flattenLets expr
binds' <- domerge binds
- return (Let (Rec binds') res)
+ return $ mkNonRecLets binds' res
where
domerge :: [(CoreBndr, CoreExpr)] -> TransformMonad [(CoreBndr, CoreExpr)]
domerge [] = return []
(bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
let bindings = concat bindingss
-- Replace the case with a let with bindings and a case
- let newlet = (Let (Rec bindings) (Case scrut b ty alts'))
+ let newlet = mkNonRecLets bindings (Case scrut b ty alts')
-- If there are no non-wild binders, or this case is already a simple
-- selector (i.e., a single alt with exactly one binding), already a simple
-- selector altan no bindings (i.e., no wild binders in the original case),
-- What transforms to run?
-transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letmergetop, letremoveunusedtop, castsimpltop]
+transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letremovetop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letmergetop, letremoveunusedtop, castsimpltop, lambdasimpltop]
-- | Returns the normalized version of the given function.
getNormalized ::
res = case resexpr of
(Var x) -> x
_ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"
-
--- | Flattens nested lets into a single list of bindings. The expression
--- passed does not have to be a let expression, if it isn't an empty list of
--- bindings is returned.
-flattenLets ::
- CoreExpr -- ^ The expression to flatten.
- -> ([Binding], CoreExpr) -- ^ The bindings and resulting expression.
-flattenLets (Let binds expr) =
- (bindings ++ bindings', expr')
- where
- -- Recursively flatten the contained expression
- (bindings', expr') =flattenLets expr
- -- Flatten our own bindings to remove the Rec / NonRec constructors
- bindings = CoreSyn.flattenBinds [binds]
-flattenLets expr = ([], expr)
projects / matthijs / master-project / cλash.git / blobdiff