X-Git-Url: https://git.stderr.nl/gitweb?a=blobdiff_plain;f=c%CE%BBash%2FCLasH%2FNormalize.hs;h=f0f2de2fccba3187092c4958bc1e3382cc0c0682;hb=ac348492299cb46ea04e15a9cecf01b4c80a3f1c;hp=1d40f92d52f7b94989fc9215bcfd15723a9001e0;hpb=4e12174b5b6515c056d4f83edcc18b991c71465d;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 1d40f92..f0f2de2 100644 --- "a/c\316\273ash/CLasH/Normalize.hs" +++ "b/c\316\273ash/CLasH/Normalize.hs" @@ -9,34 +9,27 @@ 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 -import qualified Data.Map as Map import qualified Data.Monoid as Monoid -import Data.Accessor -- GHC API import CoreSyn -import qualified UniqSupply import qualified CoreUtils import qualified Type -import qualified TcType import qualified Id import qualified Var import qualified VarSet -import qualified NameSet import qualified CoreFVs -import qualified CoreUtils import qualified MkCore -import qualified HscTypes import Outputable ( showSDoc, ppr, nest ) -- Local imports import CLasH.Normalize.NormalizeTypes import CLasH.Translator.TranslatorTypes import CLasH.Normalize.NormalizeTools -import CLasH.VHDL.VHDLTypes import qualified CLasH.Utils as Utils import CLasH.Utils.Core.CoreTools import CLasH.Utils.Core.BinderTools @@ -62,8 +55,10 @@ etatop = notappargs ("eta", eta) -- β-reduction -------------------------------- beta, betatop :: Transform --- Substitute arg for x in expr -beta (App (Lam x expr) arg) = change $ substitute [(x, arg)] expr +-- Substitute arg for x in expr. For value lambda's, also clone before +-- substitution. +beta (App (Lam x expr) arg) | CoreSyn.isTyVar x = setChanged >> substitute x arg expr + | otherwise = setChanged >> substitute_clone x arg expr -- Propagate the application into the let beta (App (Let binds expr) arg) = change $ Let binds (App expr arg) -- Propagate the application into each of the alternatives @@ -106,7 +101,7 @@ 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 @@ -114,23 +109,70 @@ castsimpl expr = return expr -- Perform this transform everywhere castsimpltop = everywhere ("castsimpl", castsimpl) + -------------------------------- --- let recursification +-- Lambda simplication -------------------------------- -letrec, letrectop :: Transform -letrec (Let (NonRec b expr) res) = change $ Let (Rec [(b, expr)]) res +-- 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 -letrec expr = return expr +lambdasimpl expr = return expr -- Perform this transform everywhere -letrectop = everywhere ("letrec", letrec) +lambdasimpltop = everywhere ("lambdasimpl", lambdasimpl) + +-------------------------------- +-- let derecursification +-------------------------------- +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 $ 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 + -- 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 +letderec expr = return expr +-- Perform this transform everywhere +letderectop = everywhere ("letderec", letderec) -------------------------------- -- let simplification -------------------------------- letsimpl, letsimpltop :: Transform +-- Don't simplify a let that evaluates to another let, since this is already +-- normal form (and would cause infinite loops with letflat below). +letsimpl expr@(Let _ (Let _ _)) = return expr -- 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 +180,7 @@ 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 @@ -152,13 +193,18 @@ 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 +-- Turn a nonrec let that binds a let into two nested lets. +letflat (Let (NonRec b (Let binds res')) res) = + change $ Let binds (Let (NonRec b res') res) 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 + -- Flatten each binding. + binds' <- Utils.concatM $ Monad.mapM flatbind binds -- 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. @@ -168,23 +214,40 @@ letflat (Let (Rec binds) expr) = do -- 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, Let (NonRec b' expr') expr) = change [(b, expr), (b', expr')] flatbind (b, expr) = return [(b, expr)] -- Leave all other expressions unchanged letflat expr = return expr -- 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 -------------------------------- -- Remove a = b bindings from let expressions everywhere -letremovetop :: Transform -letremovetop = everywhere ("letremove", inlinebind (\(b, e) -> Trans.lift $ is_local_var e)) +letremovesimpletop :: Transform +letremovesimpletop = everywhere ("letremovesimple", inlinebind (\(b, e) -> Trans.lift $ is_local_var e)) -------------------------------- -- Unused let binding removal -------------------------------- letremoveunused, letremoveunusedtop :: Transform +letremoveunused expr@(Let (NonRec b bound) res) = do + let used = expr_uses_binders [b] res + if used + then return expr + else change res letremoveunused expr@(Let (Rec binds) res) = do -- Filter out all unused binds. let binds' = filter dobind binds @@ -199,6 +262,7 @@ letremoveunused expr@(Let (Rec binds) res) = do letremoveunused expr = return expr letremoveunusedtop = everywhere ("letremoveunused", letremoveunused) +{- -------------------------------- -- Identical let binding merging -------------------------------- @@ -206,9 +270,10 @@ letremoveunusedtop = everywhere ("letremoveunused", letremoveunused) -- 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 [] @@ -228,25 +293,79 @@ letmerge expr@(Let (Rec binds) res) = do -- Leave all other expressions unchanged letmerge expr = return expr letmergetop = everywhere ("letmerge", letmerge) - +-} + -------------------------------- --- Function inlining +-- Non-representable binding inlining -------------------------------- --- Remove a = B bindings, with B :: a -> b, or B :: forall x . T, from let --- expressions everywhere. This means that any value that still needs to be --- applied to something else (polymorphic values need to be applied to a --- Type) will be inlined, and will eventually be applied to all their --- arguments. +-- Remove a = B bindings, with B of a non-representable type, from let +-- expressions everywhere. This means that any value that we can't generate a +-- signal for, will be inlined and hopefully turned into something we can +-- represent. -- -- This is a tricky function, which is prone to create loops in the -- transformations. To fix this, we make sure that no transformation will --- create a new let binding with a function type. These other transformations --- will just not work on those function-typed values at first, but the other --- transformations (in particular β-reduction) should make sure that the type --- of those values eventually becomes primitive. +-- create a new let binding with a non-representable type. These other +-- transformations will just not work on those function-typed values at first, +-- but the other transformations (in particular β-reduction) should make sure +-- that the type of those values eventually becomes representable. inlinenonreptop :: Transform inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd)) +-------------------------------- +-- Top level function inlining +-------------------------------- +-- This transformation inlines top level bindings that have been generated by +-- the compiler and are really simple. Really simple currently means that the +-- normalized form only contains a single binding, which catches most of the +-- cases where a top level function is created that simply calls a type class +-- method with a type and dictionary argument, e.g. +-- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum +-- which is later called using simply +-- fromInteger (smallInteger 10) +-- By inlining such calls to simple, compiler generated functions, we prevent +-- huge amounts of trivial components in the VHDL output, which the user never +-- wanted. We never inline user-defined functions, since we want to preserve +-- all structure defined by the user. Currently this includes all functions +-- that were created by funextract, since we would get loops otherwise. +-- +-- Note that "defined by the compiler" isn't completely watertight, since GHC +-- doesn't seem to set all those names as "system names", we apply some +-- guessing here. +inlinetoplevel, inlinetopleveltop :: Transform +-- Any system name is candidate for inlining. Never inline user-defined +-- functions, to preserve structure. +inlinetoplevel expr@(Var f) | not $ isUserDefined f = do + norm <- isNormalizeable f + -- See if this is a top level binding for which we have a body + body_maybe <- Trans.lift $ getGlobalBind f + if norm && Maybe.isJust body_maybe + then do + -- Get the normalized version + norm <- Trans.lift $ getNormalized f + if needsInline norm + then do + -- Regenerate all uniques in the to-be-inlined expression + norm_uniqued <- Trans.lift $ genUniques norm + change norm_uniqued + else + return expr + else + -- No body or not normalizeable. + return expr +-- Leave all other expressions unchanged +inlinetoplevel expr = return expr +inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel) + +needsInline :: CoreExpr -> Bool +needsInline expr = case splitNormalized expr of + -- Inline any function that only has a single definition, it is probably + -- simple enough. This might inline some stuff that it shouldn't though it + -- will never inline user-defined functions (inlinetoplevel only tries + -- system names) and inlining should never break things. + (args, [bind], res) -> True + _ -> False + -------------------------------- -- Scrutinee simplification -------------------------------- @@ -262,7 +381,7 @@ 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 @@ -270,6 +389,31 @@ scrutsimpl expr = return expr -- Perform this transform everywhere scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl) +-------------------------------- +-- Scrutinee binder removal +-------------------------------- +-- A case expression can have an extra binder, to which the scrutinee is bound +-- after bringing it to WHNF. This is used for forcing evaluation of strict +-- arguments. Since strictness does not matter for us (rather, everything is +-- sort of strict), this binder is ignored when generating VHDL, and must thus +-- be wild in the normal form. +scrutbndrremove, scrutbndrremovetop :: Transform +-- If the scrutinee is already simple, and the bndr is not wild yet, replace +-- all occurences of the binder with the scrutinee variable. +scrutbndrremove (Case (Var scrut) bndr ty alts) | bndr_used = do + alts' <- mapM subs_bndr alts + change $ Case (Var scrut) wild ty alts' + where + is_used (_, _, expr) = expr_uses_binders [bndr] expr + bndr_used = or $ map is_used alts + subs_bndr (con, bndrs, expr) = do + expr' <- substitute bndr (Var scrut) expr + return (con, bndrs, expr') + wild = MkCore.mkWildBinder (Id.idType bndr) +-- Leave all other expressions unchanged +scrutbndrremove expr = return expr +scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove) + -------------------------------- -- Case binder wildening -------------------------------- @@ -288,7 +432,7 @@ casesimpl expr@(Case scrut b ty alts) = do (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), @@ -307,11 +451,11 @@ casesimpl expr@(Case scrut b ty alts) = do -- Extract a complex expression, if possible. For this we check if any of -- the new list of bndrs are used by expr. We can't use free_vars here, -- since that looks at the old bndrs. - let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) $ expr + let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) expr (exprbinding_maybe, expr') <- doexpr expr uses_bndrs -- Create a new alternative let newalt = (con, newbndrs, expr') - let bindings = Maybe.catMaybes (exprbinding_maybe : bindings_maybe) + let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe]) return (bindings, newalt) where -- Make wild alternatives for each binder @@ -323,7 +467,7 @@ casesimpl expr@(Case scrut b ty alts) = do -- binding containing a case expression. dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr)) dobndr b i = do - repr <- isRepr (Var b) + repr <- isRepr b -- Is b wild (e.g., not a free var of expr. Since b is only in scope -- in expr, this means that b is unused if expr does not use it.) let wild = not (VarSet.elemVarSet b free_vars) @@ -358,7 +502,7 @@ casesimpl expr@(Case scrut b ty alts) = do id <- Trans.lift $ mkBinderFor expr "caseval" -- We don't flag a change here, since casevalsimpl will do that above -- based on Just we return here. - return $ (Just (id, expr), Var id) + return (Just (id, expr), Var id) else -- Don't simplify anything else return (Nothing, expr) @@ -396,7 +540,7 @@ 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 @@ -456,7 +600,7 @@ argprop expr@(App _ _) | is_var fexpr = do doarg arg = do repr <- isRepr arg bndrs <- Trans.lift getGlobalBinders - let interesting var = Var.isLocalVar var && (not $ var `elem` bndrs) + let interesting var = Var.isLocalVar var && (var `notElem` bndrs) if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg) then do -- Propagate all complex arguments that are not representable, but not @@ -472,10 +616,18 @@ argprop expr@(App _ _) | is_var fexpr = do let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg -- Mark the current expression as changed setChanged + -- TODO: Clone the free_vars (and update references in arg), since + -- this might cause conflicts if two arguments that are propagated + -- share a free variable. Also, we are now introducing new variables + -- into a function that are not fresh, which violates the binder + -- uniqueness invariant. return (map Var free_vars, free_vars, arg) else do -- Representable types will not be propagated, and arguments with free -- type variables will be propagated later. + -- Note that we implicitly remove any type variables in the type of + -- the original argument by using the type of the actual argument + -- for the new formal parameter. -- TODO: preserve original naming? id <- Trans.lift $ mkBinderFor arg "param" -- Just pass the original argument to the new function, which binds it @@ -537,6 +689,25 @@ funextract expr = return expr -- Perform this transform everywhere funextracttop = everywhere ("funextract", funextract) +-------------------------------- +-- Ensure that a function that just returns another function (or rather, +-- another top-level binder) is still properly normalized. This is a temporary +-- solution, we should probably integrate this pass with lambdasimpl and +-- letsimpl instead. +-------------------------------- +simplrestop expr@(Lam _ _) = return expr +simplrestop expr@(Let _ _) = return expr +simplrestop expr = do + local_var <- Trans.lift $ is_local_var expr + -- Don't extract values that are not representable, to prevent loops with + -- inlinenonrep + repr <- isRepr expr + if local_var || not repr + then + return expr + else do + id <- Trans.lift $ mkBinderFor expr "res" + change $ Let (NonRec id expr) (Var id) -------------------------------- -- End of transformations -------------------------------- @@ -545,14 +716,14 @@ 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 = [inlinetopleveltop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letremovetop, letsimpltop, letflattop, scrutsimpltop, scrutbndrremovetop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop, lambdasimpltop, simplrestop] -- | Returns the normalized version of the given function. getNormalized :: CoreBndr -- ^ The function to get -> TranslatorSession CoreExpr -- The normalized function body -getNormalized bndr = Utils.makeCached bndr tsNormalized $ do +getNormalized bndr = Utils.makeCached bndr tsNormalized $ if is_poly (Var bndr) then -- This should really only happen at the top level... TODO: Give @@ -569,15 +740,12 @@ 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 + expr_uniqued <- genUniques 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_uniqued ) ++ "\n") $ return () + expr' <- dotransforms transforms expr_uniqued + 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. @@ -585,7 +753,7 @@ getBinding :: CoreBndr -- ^ The binder to get the expression for -> TranslatorSession CoreExpr -- ^ The value bound to the binder -getBinding bndr = Utils.makeCached bndr tsBindings $ do +getBinding bndr = Utils.makeCached bndr tsBindings $ -- If the binding isn't in the "cache" (bindings map), then we can't create -- it out of thin air, so return an error. error $ "Normalize.getBinding: Unknown function requested: " ++ show bndr @@ -602,18 +770,3 @@ splitNormalized expr = (args, binds, res) 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)