X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Fstranal%2FWwLib.lhs;h=54248a706443980a2688c412a1062ee5dccf31ae;hb=110a35dc422a67e79baf1e101a19284dc7168908;hp=1bcf59bef674e470f56bdc494874f6da3c12f361;hpb=b4775e5e760111e2d71fba3c44882dce390edfb2;p=ghc-hetmet.git diff --git a/ghc/compiler/stranal/WwLib.lhs b/ghc/compiler/stranal/WwLib.lhs index 1bcf59b..54248a7 100644 --- a/ghc/compiler/stranal/WwLib.lhs +++ b/ghc/compiler/stranal/WwLib.lhs @@ -4,30 +4,27 @@ \section[WwLib]{A library for the ``worker/wrapper'' back-end to the strictness analyser} \begin{code} -module WwLib ( - mkWwBodies, - worthSplitting, setUnpackStrategy - ) where +module WwLib ( mkWwBodies ) where #include "HsVersions.h" import CoreSyn import CoreUtils ( exprType ) -import Id ( Id, idType, mkSysLocal, idDemandInfo, setIdDemandInfo, +import Id ( Id, idType, mkSysLocal, idNewDemandInfo, setIdNewDemandInfo, isOneShotLambda, setOneShotLambda, setIdInfo ) -import IdInfo ( CprInfo(..), vanillaIdInfo ) -import DataCon ( splitProductType ) -import Demand ( Demand(..), wwLazy, wwPrim ) -import PrelInfo ( realWorldPrimId, aBSENT_ERROR_ID ) +import IdInfo ( vanillaIdInfo ) +import DataCon ( splitProductType_maybe, splitProductType ) +import NewDemand ( Demand(..), Keepity(..), DmdResult(..) ) +import PrelInfo ( realWorldPrimId, aBSENT_ERROR_ID, eRROR_CSTRING_ID ) import TysPrim ( realWorldStatePrimTy ) import TysWiredIn ( tupleCon ) -import Type ( Type, isUnLiftedType, - splitForAllTys, splitFunTys, isAlgType, - splitNewType_maybe, mkFunTys +import Type ( Type, isUnLiftedType, mkFunTys, + splitForAllTys, splitFunTys, splitNewType_maybe, isAlgType ) -import BasicTypes ( NewOrData(..), Arity, Boxity(..) ) +import Literal ( Literal(MachStr) ) +import BasicTypes ( Arity, Boxity(..) ) import Var ( Var, isId ) import UniqSupply ( returnUs, thenUs, getUniqueUs, getUniquesUs, UniqSM ) import Util ( zipWithEqual ) @@ -42,54 +39,8 @@ import List ( zipWith4 ) %* * %************************************************************************ - ************ WARNING ****************** - these comments are rather out of date - ***************************************** - -@mkWrapperAndWorker@ is given: -\begin{enumerate} -\item -The {\em original function} \tr{f}, of the form: -\begin{verbatim} -f = /\ tyvars -> \ args -> body -\end{verbatim} -The original-binder \tr{f}, the \tr{tyvars}, \tr{args}, and \tr{body} -are given separately. - -We use the Id \tr{f} mostly to get its type. - -\item -Strictness information about \tr{f}, in the form of a list of -@Demands@. - -\item -A @UniqueSupply@. -\end{enumerate} - -@mkWrapperAndWorker@ produces (A BIT OUT-OF-DATE...): -\begin{enumerate} -\item -Maybe @Nothing@: no worker/wrappering going on in this case. This can -happen (a)~if the strictness info says that there is nothing -interesting to do or (b)~if *any* of the argument types corresponding -to ``active'' arg postitions is abstract or will be to the outside -world (i.e., {\em this} module can see the constructors, but nobody -else will be able to). An ``active'' arg position is one which the -wrapper has to unpack. An importing module can't do this unpacking, -so it simply has to give up and call the wrapper only. - -\item -Maybe \tr{Just (wrapper_Id, wrapper_body, worker_Id, worker_body)}. - -The @wrapper_Id@ is just the one that was passed in, with its -strictness IdInfo updated. -\end{enumerate} - -The \tr{body} of the original function may not be given (i.e., it's -BOTTOM), in which case you'd jolly well better not tug on the -worker-body output! - Here's an example. The original function is: + \begin{verbatim} g :: forall a . Int -> [a] -> a @@ -106,13 +57,13 @@ g :: forall a . Int -> [a] -> a g = /\ a -> \ x ys -> case x of - I# x# -> g.wrk a x# ys + I# x# -> $wg a x# ys -- call the worker; don't forget the type args! -- worker -g.wrk :: forall a . Int# -> [a] -> a +$wg :: forall a . Int# -> [a] -> a -g.wrk = /\ a -> \ x# ys -> +$wg = /\ a -> \ x# ys -> let x = I# x# in @@ -122,12 +73,14 @@ g.wrk = /\ a -> \ x# ys -> \end{verbatim} Something we have to be careful about: Here's an example: + \begin{verbatim} -- "f" strictness: U(P)U(P) f (I# a) (I# b) = a +# b g = f -- "g" strictness same as "f" \end{verbatim} + \tr{f} will get a worker all nice and friendly-like; that's good. {\em But we don't want a worker for \tr{g}}, even though it has the same strictness as \tr{f}. Doing so could break laziness, at best. @@ -141,72 +94,6 @@ the unusable strictness-info into the interfaces. %************************************************************************ %* * -\subsection{Functions over Demands} -%* * -%************************************************************************ - -\begin{code} -mAX_WORKER_ARGS :: Int -- ToDo: set via flag -mAX_WORKER_ARGS = 6 - -setUnpackStrategy :: [Demand] -> [Demand] -setUnpackStrategy ds - = snd (go (mAX_WORKER_ARGS - nonAbsentArgs ds) ds) - where - go :: Int -- Max number of args available for sub-components of [Demand] - -> [Demand] - -> (Int, [Demand]) -- Args remaining after subcomponents of [Demand] are unpacked - - go n (WwUnpack nd _ cs : ds) | n' >= 0 - = WwUnpack nd True cs' `cons` go n'' ds - | otherwise - = WwUnpack nd False cs `cons` go n ds - where - n' = n + 1 - nonAbsentArgs cs - -- Add one because we don't pass the top-level arg any more - -- Delete # of non-absent args to which we'll now be committed - (n'',cs') = go n' cs - - go n (d:ds) = d `cons` go n ds - go n [] = (n,[]) - - cons d (n,ds) = (n, d:ds) - -nonAbsentArgs :: [Demand] -> Int -nonAbsentArgs [] = 0 -nonAbsentArgs (WwLazy True : ds) = nonAbsentArgs ds -nonAbsentArgs (d : ds) = 1 + nonAbsentArgs ds - -worthSplitting :: [Demand] - -> Bool -- Result is bottom - -> Bool -- True <=> the wrapper would not be an identity function -worthSplitting ds result_bot = any worth_it ds - -- We used not to split if the result is bottom. - -- [Justification: there's no efficiency to be gained.] - -- But it's sometimes bad not to make a wrapper. Consider - -- fw = \x# -> let x = I# x# in case e of - -- p1 -> error_fn x - -- p2 -> error_fn x - -- p3 -> the real stuff - -- The re-boxing code won't go away unless error_fn gets a wrapper too. - - where - worth_it (WwLazy True) = True -- Absent arg - worth_it (WwUnpack _ True _) = True -- Arg to unpack - worth_it WwStrict = False -- Don't w/w just because of strictness - worth_it other = False - -allAbsent :: [Demand] -> Bool -allAbsent ds = all absent ds - where - absent (WwLazy is_absent) = is_absent - absent (WwUnpack _ True cs) = allAbsent cs - absent other = False -\end{code} - - -%************************************************************************ -%* * \subsection{The worker wrapper core} %* * %************************************************************************ @@ -215,11 +102,9 @@ allAbsent ds = all absent ds \begin{code} mkWwBodies :: Type -- Type of original function - -> Arity -- Arity of original function -> [Demand] -- Strictness of original function - -> Bool -- True <=> function returns bottom + -> DmdResult -- Info about function result -> [Bool] -- One-shot-ness of the function - -> CprInfo -- Result of CPR analysis -> UniqSM ([Demand], -- Demands for worker (value) args Id -> CoreExpr, -- Wrapper body, lacking only the worker Id CoreExpr -> CoreExpr) -- Worker body, lacking the original function rhs @@ -235,10 +120,10 @@ mkWwBodies :: Type -- Type of original function -- let x = (a,b) in -- E -mkWwBodies fun_ty arity demands res_bot one_shots cpr_info - = mkWWargs fun_ty arity demands' res_bot one_shots' `thenUs` \ (wrap_args, wrap_fn_args, work_fn_args, res_ty) -> - mkWWcpr res_ty cpr_info `thenUs` \ (wrap_fn_cpr, work_fn_cpr, cpr_res_ty) -> - mkWWstr cpr_res_ty wrap_args `thenUs` \ (work_dmds, wrap_fn_str, work_fn_str) -> +mkWwBodies fun_ty demands res_info one_shots + = mkWWargs fun_ty demands one_shots' `thenUs` \ (wrap_args, wrap_fn_args, work_fn_args, res_ty) -> + mkWWcpr res_ty res_info `thenUs` \ (wrap_fn_cpr, work_fn_cpr, cpr_res_ty) -> + mkWWstr cpr_res_ty wrap_args `thenUs` \ (work_dmds, wrap_fn_str, work_fn_str) -> returnUs (work_dmds, Note InlineMe . wrap_fn_args . wrap_fn_cpr . wrap_fn_str . Var, @@ -251,7 +136,6 @@ mkWwBodies fun_ty arity demands res_bot one_shots cpr_info -- f's RHS is now trivial (size 1) we still want the __inline__ to prevent -- fw from being inlined into f's RHS where - demands' = demands ++ repeat wwLazy one_shots' = one_shots ++ repeat False \end{code} @@ -293,60 +177,73 @@ the \x to get what we want. -- It chomps bites off foralls, arrows, newtypes -- and keeps repeating that until it's satisfied the supplied arity -mkWWargs :: Type -> Arity - -> [Demand] -> Bool -> [Bool] -- Both these will in due course be derived - -- from the type. The [Bool] is True for a one-shot arg. - -- ** Both are infinite, extended with neutral values if necy ** +mkWWargs :: Type + -> [Demand] + -> [Bool] -- True for a one-shot arg; ** may be infinite ** -> UniqSM ([Var], -- Wrapper args CoreExpr -> CoreExpr, -- Wrapper fn CoreExpr -> CoreExpr, -- Worker fn Type) -- Type of wrapper body -mkWWargs fun_ty arity demands res_bot one_shots - | (res_bot || arity > 0) && (not (null tyvars) || n_arg_tys > 0) - -- If the function returns bottom, we feel free to - -- build lots of wrapper args: - -- \x. let v=E in \y. bottom - -- = \xy. let v=E in bottom +mkWWargs fun_ty demands one_shots + | Just rep_ty <- splitNewType_maybe fun_ty + -- The newtype case is for when the function has + -- a recursive newtype after the arrow (rare) + -- We check for arity >= 0 to avoid looping in the case + -- of a function whose type is, in effect, infinite + -- [Arity is driven by looking at the term, not just the type.] + -- + -- It's also important when we have a function returning (say) a pair + -- wrapped in a recursive newtype, at least if CPR analysis can look + -- through such newtypes, which it probably can since they are + -- simply coerces. + = mkWWargs rep_ty demands one_shots `thenUs` \ (wrap_args, wrap_fn_args, work_fn_args, res_ty) -> + returnUs (wrap_args, + Note (Coerce fun_ty rep_ty) . wrap_fn_args, + work_fn_args . Note (Coerce rep_ty fun_ty), + res_ty) + + | not (null demands) = getUniquesUs `thenUs` \ wrap_uniqs -> let + (tyvars, tau) = splitForAllTys fun_ty + (arg_tys, body_ty) = splitFunTys tau + + n_demands = length demands + n_arg_tys = length arg_tys + n_args = n_demands `min` n_arg_tys + + new_fun_ty = mkFunTys (drop n_demands arg_tys) body_ty + new_demands = drop n_arg_tys demands + new_one_shots = drop n_args one_shots + val_args = zipWith4 mk_wrap_arg wrap_uniqs arg_tys demands one_shots wrap_args = tyvars ++ val_args in +{- ASSERT( not (null tyvars) || not (null arg_tys) ) -} + if (null tyvars) && (null arg_tys) then + pprTrace "mkWWargs" (ppr fun_ty $$ ppr demands) + returnUs ([], id, id, fun_ty) + else + mkWWargs new_fun_ty - (arity - n_args) - (drop n_args demands) - res_bot - (drop n_args one_shots) `thenUs` \ (more_wrap_args, wrap_fn_args, work_fn_args, res_ty) -> + new_demands + new_one_shots `thenUs` \ (more_wrap_args, wrap_fn_args, work_fn_args, res_ty) -> returnUs (wrap_args ++ more_wrap_args, mkLams wrap_args . wrap_fn_args, work_fn_args . applyToVars wrap_args, res_ty) - where - (tyvars, tau) = splitForAllTys fun_ty - (arg_tys, body_ty) = splitFunTys tau - n_arg_tys = length arg_tys - n_args | res_bot = n_arg_tys - | otherwise = arity `min` n_arg_tys - new_fun_ty | n_args == n_arg_tys = body_ty - | otherwise = mkFunTys (drop n_args arg_tys) body_ty - -mkWWargs fun_ty arity demands res_bot one_shots - = case splitNewType_maybe fun_ty of - Nothing -> returnUs ([], id, id, fun_ty) - Just rep_ty -> mkWWargs rep_ty arity demands res_bot one_shots `thenUs` \ (wrap_args, wrap_fn_args, work_fn_args, res_ty) -> - returnUs (wrap_args, - Note (Coerce fun_ty rep_ty) . wrap_fn_args, - work_fn_args . Note (Coerce rep_ty fun_ty), - res_ty) + + | otherwise + = returnUs ([], id, id, fun_ty) applyToVars :: [Var] -> CoreExpr -> CoreExpr applyToVars vars fn = mkVarApps fn vars mk_wrap_arg uniq ty dmd one_shot - = set_one_shot one_shot (setIdDemandInfo (mkSysLocal SLIT("w") uniq ty) dmd) + = set_one_shot one_shot (setIdNewDemandInfo (mkSysLocal SLIT("w") uniq ty) dmd) where set_one_shot True id = setOneShotLambda id set_one_shot False id = id @@ -375,12 +272,12 @@ mkWWstr :: Type -- Result type mkWWstr res_ty wrap_args = mk_ww_str wrap_args `thenUs` \ (work_args, take_apart, put_together) -> let - work_dmds = [idDemandInfo v | v <- work_args, isId v] + work_dmds = [idNewDemandInfo v | v <- work_args, isId v] apply_to args fn = mkVarApps fn args in if not (null work_dmds && isUnLiftedType res_ty) then returnUs ( work_dmds, - take_apart . apply_to work_args, + take_apart . applyToVars work_args, mkLams work_args . put_together) else -- Horrid special case. If the worker would have no arguments, and the @@ -395,8 +292,8 @@ mkWWstr res_ty wrap_args let void_arg = mk_ww_local void_arg_uniq realWorldStatePrimTy in - returnUs ([wwPrim], - take_apart . apply_to [realWorldPrimId] . apply_to work_args, + returnUs ([Lazy], + take_apart . applyToVars [realWorldPrimId] . apply_to work_args, mkLams work_args . Lam void_arg . put_together) -- Empty case @@ -412,26 +309,47 @@ mk_ww_str (arg : ds) returnUs (arg : worker_args, wrap_fn, work_fn) | otherwise - = case idDemandInfo arg of + = case idNewDemandInfo arg of - -- Absent case - WwLazy True -> + -- Absent case. We don't deal with absence for unlifted types, + -- though, because it's not so easy to manufacture a placeholder + -- We'll see if this turns out to be a problem + Abs | not (isUnLiftedType (idType arg)) -> mk_ww_str ds `thenUs` \ (worker_args, wrap_fn, work_fn) -> returnUs (worker_args, wrap_fn, mk_absent_let arg . work_fn) + -- Seq and keep + Seq Keep _ [] -> mk_ww_str ds `thenUs` \ (worker_args, wrap_fn, work_fn) -> + returnUs (arg : worker_args, mk_seq_case arg . wrap_fn, work_fn) + -- Pass the arg, no need to rebox + + -- Seq and discard + Seq Drop _ [] -> mk_ww_str ds `thenUs` \ (worker_args, wrap_fn, work_fn) -> + returnUs (worker_args, mk_seq_case arg . wrap_fn, mk_absent_let arg . work_fn) + -- Don't pass the arg, build absent arg + -- Unpack case - WwUnpack new_or_data True cs -> - getUniquesUs `thenUs` \ uniqs -> - let - unpk_args = zipWith mk_ww_local uniqs inst_con_arg_tys - unpk_args_w_ds = zipWithEqual "mk_ww_str" set_worker_arg_info unpk_args cs - in - mk_ww_str (unpk_args_w_ds ++ ds) `thenUs` \ (worker_args, wrap_fn, work_fn) -> - returnUs (worker_args, - mk_unpk_case new_or_data arg unpk_args data_con arg_tycon . wrap_fn, - work_fn . mk_pk_let new_or_data arg data_con tycon_arg_tys unpk_args) - where - (arg_tycon, tycon_arg_tys, data_con, inst_con_arg_tys) = splitProductType "mk_ww_str" (idType arg) + Seq keep _ cs + | Just (arg_tycon, tycon_arg_tys, data_con, inst_con_arg_tys) + <- splitProductType_maybe (idType arg) + -> getUniquesUs `thenUs` \ uniqs -> + let + unpk_args = zipWith mk_ww_local uniqs inst_con_arg_tys + unpk_args_w_ds = zipWithEqual "mk_ww_str" set_worker_arg_info unpk_args cs + unbox_fn = mk_unpk_case arg unpk_args data_con arg_tycon + rebox_fn = mk_pk_let arg data_con tycon_arg_tys unpk_args + in + mk_ww_str (unpk_args_w_ds ++ ds) `thenUs` \ (worker_args, wrap_fn, work_fn) -> + case keep of + Keep -> returnUs (arg : worker_args, unbox_fn . wrap_fn, work_fn) + -- Pass the arg, no need to rebox + Drop -> returnUs (worker_args, unbox_fn . wrap_fn, work_fn . rebox_fn) + -- Don't pass the arg, rebox instead + + | otherwise -> + WARN( True, ppr arg ) + mk_ww_str ds `thenUs` \ (worker_args, wrap_fn, work_fn) -> + returnUs (arg : worker_args, wrap_fn, work_fn) -- Other cases other_demand -> @@ -441,7 +359,7 @@ mk_ww_str (arg : ds) -- If the wrapper argument is a one-shot lambda, then -- so should (all) the corresponding worker arguments be -- This bites when we do w/w on a case join point - set_worker_arg_info worker_arg demand = set_one_shot (setIdDemandInfo worker_arg demand) + set_worker_arg_info worker_arg demand = set_one_shot (setIdNewDemandInfo worker_arg demand) set_one_shot | isOneShotLambda arg = setOneShotLambda | otherwise = \x -> x @@ -466,15 +384,12 @@ left-to-right traversal of the result structure. \begin{code} mkWWcpr :: Type -- function body type - -> CprInfo -- CPR analysis results + -> DmdResult -- CPR analysis results -> UniqSM (CoreExpr -> CoreExpr, -- New wrapper CoreExpr -> CoreExpr, -- New worker Type) -- Type of worker's body -mkWWcpr body_ty NoCPRInfo - = returnUs (id, id, body_ty) -- Must be just the strictness transf. - -mkWWcpr body_ty ReturnsCPR +mkWWcpr body_ty RetCPR | not (isAlgType body_ty) = WARN( True, text "mkWWcpr: non-algebraic body type" <+> ppr body_ty ) returnUs (id, id, body_ty) @@ -508,6 +423,9 @@ mkWWcpr body_ty ReturnsCPR n_con_args = length con_arg_tys con_arg_ty1 = head con_arg_tys +mkWWcpr body_ty other -- No CPR info + = returnUs (id, id, body_ty) + -- If the original function looked like -- f = \ x -> _scc_ "foo" E -- @@ -534,27 +452,23 @@ workerCase e arg alts = Case e arg alts \begin{code} mk_absent_let arg body | not (isUnLiftedType arg_ty) - = Let (NonRec arg (mkTyApps (Var aBSENT_ERROR_ID) [arg_ty])) body + = Let (NonRec arg abs_rhs) body | otherwise = panic "WwLib: haven't done mk_absent_let for primitives yet" where arg_ty = idType arg +-- abs_rhs = mkTyApps (Var aBSENT_ERROR_ID) [arg_ty] + abs_rhs = mkApps (Var eRROR_CSTRING_ID) [Type arg_ty, Lit (MachStr (_PK_ msg))] + msg = "Oops! Entered absent arg " ++ showSDocDebug (ppr arg <+> ppr (idType arg)) -mk_unpk_case NewType arg unpk_args boxing_con boxing_tycon body - -- A newtype! Use a coercion not a case - = ASSERT( null other_args ) - Case (Note (Coerce (idType unpk_arg) (idType arg)) (Var arg)) - (sanitiseCaseBndr unpk_arg) - [(DEFAULT,[],body)] - where - (unpk_arg:other_args) = unpk_args - -mk_unpk_case DataType arg unpk_args boxing_con boxing_tycon body +mk_unpk_case arg unpk_args boxing_con boxing_tycon body -- A data type = Case (Var arg) (sanitiseCaseBndr arg) [(DataAlt boxing_con, unpk_args, body)] +mk_seq_case arg body = Case (Var arg) (sanitiseCaseBndr arg) [(DEFAULT, [], body)] + sanitiseCaseBndr :: Id -> Id -- The argument we are scrutinising has the right type to be -- a case binder, so it's convenient to re-use it for that purpose. @@ -566,18 +480,10 @@ sanitiseCaseBndr :: Id -> Id -- like (x+y) `seq` .... sanitiseCaseBndr id = id `setIdInfo` vanillaIdInfo -mk_pk_let NewType arg boxing_con con_tys unpk_args body - = ASSERT( null other_args ) - Let (NonRec arg (Note (Coerce (idType arg) (idType unpk_arg)) (Var unpk_arg))) body - where - (unpk_arg:other_args) = unpk_args - -mk_pk_let DataType arg boxing_con con_tys unpk_args body +mk_pk_let arg boxing_con con_tys unpk_args body = Let (NonRec arg (mkConApp boxing_con con_args)) body where con_args = map Type con_tys ++ map Var unpk_args - mk_ww_local uniq ty = mkSysLocal SLIT("ww") uniq ty - \end{code}