X-Git-Url: https://git.stderr.nl/gitweb?a=blobdiff_plain;f=c%CE%BBash%2FCLasH%2FNormalize.hs;h=07ded20bbb8d387c38372f749c9c79789d38cdbf;hb=78793ddabc41998c386589564d6c47411279b29f;hp=7fb0dc235d2a60d8a3e3798b8a655e9f6f3218f7;hpb=10dfe589f40e65d51ca1585beecf00ae85169cae;p=matthijs%2Fmaster-project%2Fc%CE%BBash.git diff --git "a/c\316\273ash/CLasH/Normalize.hs" "b/c\316\273ash/CLasH/Normalize.hs" index 7fb0dc2..07ded20 100644 --- "a/c\316\273ash/CLasH/Normalize.hs" +++ "b/c\316\273ash/CLasH/Normalize.hs" @@ -9,6 +9,7 @@ module CLasH.Normalize (getNormalized, normalizeExpr, splitNormalized) where -- Standard modules import Debug.Trace import qualified Maybe +import qualified List import qualified "transformers" Control.Monad.Trans as Trans import qualified Control.Monad as Monad import qualified Control.Monad.Trans.Writer as Writer @@ -106,7 +107,7 @@ castsimpl expr@(Cast val ty) = do -- Generate a binder for the expression id <- Trans.lift $ mkBinderFor val "castval" -- Extract the expression - change $ Let (Rec [(id, val)]) (Cast (Var id) ty) + change $ Let (NonRec id val) (Cast (Var id) ty) else return expr -- Leave all other expressions unchanged @@ -115,14 +116,31 @@ castsimpl expr = return expr castsimpltop = everywhere ("castsimpl", castsimpl) -------------------------------- --- let recursification +-- let derecursification -------------------------------- -letrec, letrectop :: Transform -letrec (Let (NonRec b expr) res) = change $ Let (Rec [(b, expr)]) res +letderec, letderectop :: Transform +letderec expr@(Let (Rec binds) res) = case liftable of + -- Nothing is liftable, just return + [] -> return expr + -- Something can be lifted, generate a new let expression + _ -> change $ MkCore.mkCoreLets newbinds 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 + -- single bind recursive let. + canlift (bndr, e) = not $ expr_uses_binders bndrs e -- Leave all other expressions unchanged -letrec expr = return expr +letderec expr = return expr -- Perform this transform everywhere -letrectop = everywhere ("letrec", letrec) +letderectop = everywhere ("letderec", letderec) -------------------------------- -- let simplification @@ -130,7 +148,7 @@ letrectop = everywhere ("letrec", letrec) letsimpl, letsimpltop :: Transform -- Put the "in ..." value of a let in its own binding, but not when the -- expression is already a local variable, or not representable (to prevent loops with inlinenonrep). -letsimpl expr@(Let (Rec binds) res) = do +letsimpl expr@(Let binds res) = do repr <- isRepr res local_var <- Trans.lift $ is_local_var res if not local_var && repr @@ -138,8 +156,7 @@ letsimpl expr@(Let (Rec binds) res) = do -- If the result is not a local var already (to prevent loops with -- ourselves), extract it. id <- Trans.lift $ mkBinderFor res "foo" - let bind = (id, res) - change $ Let (Rec (bind:binds)) (Var id) + change $ Let binds (Let (NonRec id res) (Var id)) else -- If the result is already a local var, don't extract it. return expr @@ -152,23 +169,14 @@ letsimpltop = everywhere ("letsimpl", letsimpl) -------------------------------- -- let flattening -------------------------------- +-- Takes a let that binds another let, and turns that into two nested lets. +-- e.g., from: +-- let b = (let b' = expr' in res') in res +-- to: +-- let b' = expr' in (let b = res' in res) letflat, letflattop :: Transform -letflat (Let (Rec binds) expr) = do - -- Turn each binding into a list of bindings (possibly containing just one - -- element, of course) - bindss <- Monad.mapM flatbind binds - -- Concat all the bindings - let binds' = concat bindss - -- Return the new let. We don't use change here, since possibly nothing has - -- changed. If anything has changed, flatbind has already flagged that - -- change. - return $ Let (Rec binds') expr - where - -- Turns a binding of a let into a multiple bindings, or any other binding - -- into a list with just that binding - flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)] - flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds) - flatbind (b, expr) = return [(b, expr)] +letflat (Let (NonRec b (Let (NonRec b' expr') res')) res) = + change $ Let (NonRec b' expr') (Let (NonRec b res') res) -- Leave all other expressions unchanged letflat expr = return expr -- Perform this transform everywhere @@ -262,7 +270,7 @@ scrutsimpl expr@(Case scrut b ty alts) = do if repr then do id <- Trans.lift $ mkBinderFor scrut "scrut" - change $ Let (Rec [(id, scrut)]) (Case (Var id) b ty alts) + change $ Let (NonRec id scrut) (Case (Var id) b ty alts) else return expr -- Leave all other expressions unchanged @@ -396,7 +404,7 @@ appsimpl expr@(App f arg) = do if repr && not local_var then do -- Extract representable arguments id <- Trans.lift $ mkBinderFor arg "arg" - change $ Let (Rec [(id, arg)]) (App f (Var id)) + change $ Let (NonRec id arg) (App f (Var id)) else -- Leave non-representable arguments unchanged return expr -- Leave all other expressions unchanged @@ -545,7 +553,7 @@ funextracttop = everywhere ("funextract", funextract) -- What transforms to run? -transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letmergetop, letremoveunusedtop, castsimpltop] +transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letderectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letmergetop, letremoveunusedtop, castsimpltop] -- | Returns the normalized version of the given function. getNormalized :: @@ -569,15 +577,11 @@ normalizeExpr :: -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression normalizeExpr what expr = do - -- Introduce an empty Let at the top level, so there will always be - -- a let in the expression (none of the transformations will remove - -- the last let). - let expr' = Let (Rec []) expr -- Normalize this expression - trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr' ) ++ "\n") $ return () - expr'' <- dotransforms transforms expr' - trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr'')) $ return () - return expr'' + trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr ) ++ "\n") $ return () + expr' <- dotransforms transforms expr + trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')) $ return () + return expr' -- | Get the value that is bound to the given binder at top level. Fails when -- there is no such binding. @@ -595,9 +599,25 @@ getBinding bndr = Utils.makeCached bndr tsBindings $ do splitNormalized :: CoreExpr -- ^ The normalized expression -> ([CoreBndr], [Binding], CoreBndr) -splitNormalized expr = - case letexpr of - (Let (Rec binds) (Var res)) -> (args, binds, res) - _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n" +splitNormalized expr = (args, binds, res) where (args, letexpr) = CoreSyn.collectBinders expr + (binds, resexpr) = flattenLets letexpr + 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)