From: Matthijs Kooijman Date: Fri, 31 Jul 2009 12:34:34 +0000 (+0200) Subject: Merge casevalsimpl and casewild into casesimpl. X-Git-Url: https://git.stderr.nl/gitweb?a=commitdiff_plain;h=1f94e5a3010ebce788762ab08ce022d3f7d8f033;p=matthijs%2Fmaster-project%2Fc%CE%BBash.git Merge casevalsimpl and casewild into casesimpl. Both transformations had a very similar structure, which are now merged. --- diff --git "a/c\316\273ash/CLasH/Normalize.hs" "b/c\316\273ash/CLasH/Normalize.hs" index c651f8a..8ec195b 100644 --- "a/c\316\273ash/CLasH/Normalize.hs" +++ "b/c\316\273ash/CLasH/Normalize.hs" @@ -198,13 +198,18 @@ scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl) -------------------------------- -- Case binder wildening -------------------------------- -casewild, casewildtop :: Transform --- Make sure that all case alternatives have only wild binders, except for --- simple selector cases (e.g., case x of (a, ) -> a). This is done by --- creating a new let binding for each non-wild binder, which is bound to a --- new simple selector case statement. We do this only for binders with a --- representable type, to prevent loops with inlinenonrep. -casewild expr@(Case scrut b ty alts) = do +casesimpl, casesimpltop :: Transform +-- This is already a selector case (or, if x does not appear in bndrs, a very +-- simple case statement that will be removed by caseremove below). Just leave +-- it be. +casesimpl expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr +-- Make sure that all case alternatives have only wild binders and simple +-- expressions. +-- This is done by creating a new let binding for each non-wild binder, which +-- is bound to a new simple selector case statement and for each complex +-- expression. We do this only for representable types, to prevent loops with +-- inlinenonrep. +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 @@ -213,7 +218,7 @@ casewild expr@(Case scrut b ty alts) = do -- 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), -- don't change anything, otherwise, replace the case. - if null bindings || length alts == 1 && length bindings == 1 then return expr else change newlet + if null bindings then return expr else change newlet where -- Generate a single wild binder, since they are all the same wild = MkCore.mkWildBinder @@ -221,31 +226,35 @@ casewild expr@(Case scrut b ty alts) = do -- sideeffect. doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt) doalt (con, bndrs, expr) = do - extracts <- Monad.zipWithM mkextracts bndrs [0..] - let (newbndrs, bindings_maybe) = unzip extracts - let bindings = Maybe.catMaybes bindings_maybe - -- Note that we leave expr unchanged, even though most binders will have - -- become wild. The binders that were previously bound by the case - -- alternative, will now be bound in a surrounding let expression (e.g., - -- by bindings). - let newalt = (con, newbndrs, expr) + -- Make each binder wild, if possible + bndrs_res <- Monad.zipWithM dobndr bndrs [0..] + let (newbndrs, bindings_maybe) = unzip bndrs_res + -- 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 + (exprbinding_maybe, expr') <- doexpr expr uses_bndrs + -- Create a new alternative + let newalt = (con, newbndrs, expr') + let bindings = Maybe.catMaybes (exprbinding_maybe : bindings_maybe) return (bindings, newalt) where - -- Make all binders wild + -- Make wild alternatives for each binder wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs -- A set of all the binders that are used by the expression free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr -- Look at the ith binder in the case alternative. Return a new binder -- for it (either the same one, or a wild one) and optionally a let - -- binding with a case expression. - mkextracts :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr)) - mkextracts b i = do + -- binding containing a case expression. + dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr)) + dobndr b i = do repr <- isRepr (Var 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) -- Create a new binding for any representable binder that is not - -- already wild. + -- already wild and is representable (to prevent loops with + -- inlinenonrep). if (not wild) && repr then do -- Create on new binder that will actually capture a value in this @@ -259,52 +268,29 @@ casewild expr@(Case scrut b ty alts) = do -- Just leave the original binder in place, and don't generate an -- extra selector case. return (b, Nothing) + -- Process the expression of a case alternative. Accepts an expression + -- and whether this expression uses any of the binders in the + -- alternative. Returns an optional new binding and a new expression. + doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr) + doexpr expr uses_bndrs = do + local_var <- Trans.lift $ is_local_var expr + repr <- isRepr expr + -- Extract any expressions that do not use any binders from this + -- alternative, is not a local var already and is representable (to + -- prevent loops with inlinenonrep). + if (not uses_bndrs) && (not local_var) && repr + then do + id <- mkInternalVar "caseval" (CoreUtils.exprType expr) + -- 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) + else + -- Don't simplify anything else + return (Nothing, expr) -- Leave all other expressions unchanged -casewild expr = return expr --- Perform this transform everywhere -casewildtop = everywhere ("casewild", casewild) - --------------------------------- --- Case value simplification --------------------------------- -casevalsimpl, casevalsimpltop :: Transform -casevalsimpl expr@(Case scrut b ty alts) = do - -- Try to simplify each alternative, resulting in an optional binding and a - -- new alternative. - (bindings_maybe, alts') <- (Monad.liftM unzip) $ mapM doalt alts - let bindings = Maybe.catMaybes bindings_maybe - -- Create a new let around the case, that binds of the cases values. - let newlet = Let (Rec bindings) (Case scrut b ty alts') - -- If there were no values that needed and allowed simplification, don't - -- change the case. - if null bindings then return expr else change newlet - where - doalt :: CoreAlt -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreAlt) - -- Don't simplify values that are already simple - doalt alt@(con, bndrs, Var _) = return (Nothing, alt) - -- Simplify each alt by creating a new id, binding the case value to it and - -- replacing the case value with that id. Only do this when the case value - -- does not use any of the binders bound by this alternative, for that would - -- cause those binders to become unbound when moving the value outside of - -- the case statement. Also, don't create a binding for non-representable - -- expressions, to prevent loops with inlinenonrep. - doalt alt@(con, bndrs, expr) = do - repr <- isRepr expr - -- Find if any of the binders are used by expr - let usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr - if (not usesvars && repr) - then do - id <- mkInternalVar "caseval" (CoreUtils.exprType expr) - -- We don't flag a change here, since casevalsimpl will do that above - -- based on Just we return here. - return $ (Just (id, expr), (con, bndrs, Var id)) - else - -- Don't simplify anything else - return (Nothing, alt) --- Leave all other expressions unchanged -casevalsimpl expr = return expr +casesimpl expr = return expr -- Perform this transform everywhere -casevalsimpltop = everywhere ("casevalsimpl", casevalsimpl) +casesimpltop = everywhere ("casesimpl", casesimpl) -------------------------------- -- Case removal @@ -484,7 +470,7 @@ funextracttop = everywhere ("funextract", funextract) -- What transforms to run? -transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, casewildtop, scrutsimpltop, casevalsimpltop, caseremovetop, inlinenonreptop, appsimpltop] +transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop] -- Turns the given bind into VHDL normalizeModule ::