X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Fstranal%2FWwLib.lhs;h=e1a1da6463532f6490298a0d1515ec719cbafccc;hb=d1652879c78b51f3caf7ffb9e49460012629fa62;hp=4eefd47a1907025389f319a27ccba8f84b887244;hpb=9d38678ea60ff32f756390a30c659daa22c98c93;p=ghc-hetmet.git diff --git a/ghc/compiler/stranal/WwLib.lhs b/ghc/compiler/stranal/WwLib.lhs index 4eefd47..e1a1da6 100644 --- a/ghc/compiler/stranal/WwLib.lhs +++ b/ghc/compiler/stranal/WwLib.lhs @@ -4,66 +4,32 @@ \section[WwLib]{A library for the ``worker/wrapper'' back-end to the strictness analyser} \begin{code} -module WwLib ( - WwBinding(..), - - worthSplitting, setUnpackStrategy, - mkWwBodies, mkWrapper - ) where +module WwLib ( mkWwBodies, mkWWstr, mkWorkerArgs ) where #include "HsVersions.h" import CoreSyn -import Id ( Id, idType, mkSysLocal, getIdDemandInfo, setIdDemandInfo, - mkWildId, setIdInfo +import CoreUtils ( exprType ) +import Id ( Id, idType, mkSysLocal, idNewDemandInfo, setIdNewDemandInfo, + isOneShotLambda, setOneShotLambda, setIdUnfolding, + setIdInfo ) -import IdInfo ( CprInfo(..), noCprInfo, vanillaIdInfo ) -import Const ( Con(..), DataCon ) -import DataCon ( dataConArgTys ) -import Demand ( Demand(..) ) -import PrelInfo ( realWorldPrimId, aBSENT_ERROR_ID ) -import TysPrim ( realWorldStatePrimTy ) -import TysWiredIn ( unboxedTupleCon, unboxedTupleTyCon ) -import Type ( isUnLiftedType, mkTyVarTys, mkTyVarTy, mkFunTys, - splitForAllTys, splitFunTys, splitFunTysN, - splitAlgTyConApp_maybe, splitAlgTyConApp, - mkTyConApp, newTypeRep, isNewType, - Type +import IdInfo ( vanillaIdInfo ) +import DataCon ( splitProductType_maybe, splitProductType ) +import NewDemand ( Demand(..), DmdResult(..), Demands(..) ) +import MkId ( realWorldPrimId, voidArgId, mkRuntimeErrorApp, rUNTIME_ERROR_ID ) +import TysWiredIn ( tupleCon ) +import Type ( Type, isUnLiftedType, mkFunTys, + splitForAllTys, splitFunTys, splitRecNewType_maybe, isAlgType ) -import TyCon ( isNewTyCon, - TyCon ) -import BasicTypes ( NewOrData(..) ) -import Var ( TyVar ) -import UniqSupply ( returnUs, thenUs, getUniqueUs, getUniquesUs, - mapUs, UniqSM ) -import Util ( zipWithEqual, zipEqual ) +import BasicTypes ( Boxity(..) ) +import Var ( Var, isId ) +import UniqSupply ( returnUs, thenUs, getUniquesUs, UniqSM ) +import Util ( zipWithEqual, notNull ) import Outputable +import List ( zipWith4 ) \end{code} -%************************************************************************ -%* * -\subsection[datatype-WwLib]{@WwBinding@: a datatype for worker/wrapper-ing} -%* * -%************************************************************************ - -In the worker/wrapper stuff, we want to carry around @CoreBindings@ in -an ``intermediate form'' that can later be turned into a \tr{let} or -\tr{case} (depending on strictness info). - -\begin{code} -data WwBinding - = WwLet [CoreBind] - | WwCase (CoreExpr -> CoreExpr) - -- the "case" will be a "strict let" of the form: - -- - -- case rhs of - -- -> body - -- - -- (instead of "let = rhs in body") - -- - -- The expr you pass to the function is "body" (the - -- expression that goes "in the corner"). -\end{code} %************************************************************************ %* * @@ -71,54 +37,8 @@ data WwBinding %* * %************************************************************************ - ************ 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 @@ -135,13 +55,13 @@ 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 @@ -151,12 +71,14 @@ 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. @@ -170,128 +92,88 @@ the unusable strictness-info into the interfaces. %************************************************************************ %* * -\subsection{Functions over Demands} +\subsection{The worker wrapper core} %* * %************************************************************************ -\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 = not result_bot && any worth_it ds - -- Don't split if the result is bottom; there's no efficiency to - -- be gained, and (worse) the wrapper body may not look like a wrapper - -- body to getWorkerIdAndCons - 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 +@mkWwBodies@ is called when doing the worker/wrapper split inside a module. -allAbsent :: [Demand] -> Bool -allAbsent ds = all absent ds +\begin{code} +mkWwBodies :: Type -- Type of original function + -> [Demand] -- Strictness of original function + -> DmdResult -- Info about function result + -> [Bool] -- One-shot-ness of the function + -> 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 + +-- wrap_fn_args E = \x y -> E +-- work_fn_args E = E x y + +-- wrap_fn_str E = case x of { (a,b) -> +-- case a of { (a1,a2) -> +-- E a1 a2 b y }} +-- work_fn_str E = \a2 a2 b y -> +-- let a = (a1,a2) in +-- let x = (a,b) in +-- E + +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) -> + mkWWstr wrap_args `thenUs` \ (work_args, wrap_fn_str, work_fn_str) -> + let + (work_lam_args, work_call_args) = mkWorkerArgs work_args res_ty + in + -- Don't do CPR if the worker doesn't have any value arguments + -- Then the worker is just a constant, so we don't want to unbox it. + (if any isId work_args then + mkWWcpr res_ty res_info + else + returnUs (id, id, res_ty) + ) `thenUs` \ (wrap_fn_cpr, work_fn_cpr, cpr_res_ty) -> + + returnUs ([idNewDemandInfo v | v <- work_args, isId v], + Note InlineMe . wrap_fn_args . wrap_fn_cpr . wrap_fn_str . applyToVars work_call_args . Var, + mkLams work_lam_args. work_fn_str . work_fn_cpr . work_fn_args) + -- We use an INLINE unconditionally, even if the wrapper turns out to be + -- something trivial like + -- fw = ... + -- f = __inline__ (coerce T fw) + -- The point is to propagate the coerce to f's call sites, so even though + -- f's RHS is now trivial (size 1) we still want the __inline__ to prevent + -- fw from being inlined into f's RHS where - absent (WwLazy is_absent) = is_absent - absent (WwUnpack _ True cs) = allAbsent cs - absent other = False + one_shots' = one_shots ++ repeat False \end{code} %************************************************************************ %* * -\subsection{The worker wrapper core} +\subsection{Making wrapper args} %* * %************************************************************************ -@mkWrapper@ is called when importing a function. We have the type of -the function and the name of its worker, and we want to make its body (the wrapper). +During worker-wrapper stuff we may end up with an unlifted thing +which we want to let-bind without losing laziness. So we +add a void argument. E.g. -\begin{code} -mkWrapper :: Type -- Wrapper type - -> Int -- Arity - -> [Demand] -- Wrapper strictness info - -> CprInfo -- Wrapper cpr info - -> UniqSM (Id -> CoreExpr) -- Wrapper body, missing worker Id - -mkWrapper fun_ty arity demands cpr_info - = getUniquesUs arity `thenUs` \ wrap_uniqs -> - let - (tyvars, tau_ty) = splitForAllTys fun_ty - (arg_tys, body_ty) = splitFunTysN "mkWrapper" arity tau_ty - -- The "expanding dicts" part here is important, even for the splitForAll - -- The imported thing might be a dictionary, such as Functor Foo - -- But Functor Foo = forall a b. (a->b) -> Foo a -> Foo b - -- and as such might have some strictness info attached. - -- Then we need to have enough args to zip to the strictness info - - wrap_args = zipWith mk_ww_local wrap_uniqs arg_tys - in - mkWwBodies tyvars wrap_args body_ty demands cpr_info `thenUs` \ (wrap_fn, _, _) -> - returnUs wrap_fn -\end{code} + f = /\a -> \x y z -> E::Int# -- E does not mention x,y,z +==> + fw = /\ a -> \void -> E + f = /\ a -> \x y z -> fw realworld -@mkWwBodies@ is called when doing the worker/wrapper split inside a module. +We use the state-token type which generates no code. \begin{code} -mkWwBodies :: [TyVar] -> [Id] -> Type -- Original fn args and body type - -> [Demand] -- Strictness info for original fn; corresp 1-1 with args - -> CprInfo -- Result of CPR analysis - -> UniqSM (Id -> CoreExpr, -- Wrapper body, lacking only the worker Id - CoreExpr -> CoreExpr, -- Worker body, lacking the original function body - [Demand]) -- Strictness info for worker - -mkWwBodies tyvars wrap_args body_ty demands cpr_info - = let - -- demands may be longer than number of args. If we aren't doing w/w - -- for strictness then demands is an infinite list of 'lazy' args. - wrap_args_w_demands = zipWith setIdDemandInfo wrap_args demands - (wrap_fn_coerce, work_fn_coerce) = mkWWcoerce body_ty - in - mkWWstr body_ty wrap_args_w_demands `thenUs` \ (work_args_w_demands, wrap_fn_str, work_fn_str) -> - - mkWWcpr body_ty cpr_info `thenUs` \ (wrap_fn_cpr, work_fn_cpr) -> - - returnUs (\ work_id -> Note InlineMe $ - mkLams tyvars $ mkLams wrap_args_w_demands $ - (wrap_fn_coerce . wrap_fn_str . wrap_fn_cpr) $ - mkVarApps (Var work_id) (tyvars ++ work_args_w_demands), - - \ work_body -> mkLams tyvars $ mkLams work_args_w_demands $ - (work_fn_coerce . work_fn_str . work_fn_cpr) - work_body, - - map getIdDemandInfo work_args_w_demands) +mkWorkerArgs :: [Var] + -> Type -- Type of body + -> ([Var], -- Lambda bound args + [Var]) -- Args at call site +mkWorkerArgs args res_ty + | any isId args || not (isUnLiftedType res_ty) + = (args, args) + | otherwise + = (args ++ [voidArgId], args ++ [realWorldPrimId]) \end{code} @@ -301,30 +183,109 @@ mkWwBodies tyvars wrap_args body_ty demands cpr_info %* * %************************************************************************ -The "coerce" transformation is - f :: T1 -> T2 -> R - f = \xy -> e -===> - f = \xy -> coerce R R' (fw x y) - fw = \xy -> coerce R' R e -where R' is the representation type for R. +We really want to "look through" coerces. +Reason: I've seen this situation: + + let f = coerce T (\s -> E) + in \x -> case x of + p -> coerce T' f + q -> \s -> E2 + r -> coerce T' f + +If only we w/w'd f, we'd get + let f = coerce T (\s -> fw s) + fw = \s -> E + in ... + +Now we'll inline f to get + + let fw = \s -> E + in \x -> case x of + p -> fw + q -> \s -> E2 + r -> fw + +Now we'll see that fw has arity 1, and will arity expand +the \x to get what we want. \begin{code} -mkWWcoerce body_ty - | not (isNewType body_ty) - = (id, id) +-- mkWWargs is driven off the function type and arity. +-- It chomps bites off foralls, arrows, newtypes +-- and keeps repeating that until it's satisfied the supplied arity + +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 demands one_shots + | Just rep_ty <- splitRecNewType_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) + + | notNull 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( notNull tyvars || notNull 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 + 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) | otherwise - = (wrap_fn . mkNote (Coerce body_ty rep_ty), - mkNote (Coerce rep_ty body_ty) . work_fn) - where - (tycon, args, _) = splitAlgTyConApp body_ty - rep_ty = newTypeRep tycon args - (wrap_fn, work_fn) = mkWWcoerce rep_ty -\end{code} + = 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 (setIdNewDemandInfo (mkSysLocal FSLIT("w") uniq ty) dmd) + where + set_one_shot True id = setOneShotLambda id + set_one_shot False id = id +\end{code} + %************************************************************************ %* * @@ -332,90 +293,100 @@ mkWWcoerce body_ty %* * %************************************************************************ - \begin{code} -mkWWstr :: Type -- Body type - -> [Id] -- Wrapper args; have their demand info on them - -> UniqSM ([Id], -- Worker args; have their demand info on them - - CoreExpr -> CoreExpr, -- Wrapper body, lacking the inner call to the worker +mkWWstr :: [Var] -- Wrapper args; have their demand info on them + -- *Includes type variables* + -> UniqSM ([Var], -- Worker args + CoreExpr -> CoreExpr, -- Wrapper body, lacking the worker call -- and without its lambdas - -- At the call site, the worker args are bound + -- This fn adds the unboxing CoreExpr -> CoreExpr) -- Worker body, lacking the original body of the function, - -- and without its lambdas + -- and lacking its lambdas. + -- This fn does the reboxing -mkWWstr body_ty wrap_args - = mk_ww wrap_args `thenUs` \ (work_args, wrap_fn, work_fn) -> +---------------------- +nop_fn body = body - if null work_args && isUnLiftedType body_ty then - -- Horrid special case. If the worker would have no arguments, and the - -- function returns a primitive type value, that would make the worker into - -- an unboxed value. We box it by passing a dummy void argument, thus: - -- - -- f = /\abc. \xyz. fw abc void - -- fw = /\abc. \v. body - -- - -- We use the state-token type which generates no code - getUniqueUs `thenUs` \ void_arg_uniq -> - let - void_arg = mk_ww_local void_arg_uniq realWorldStatePrimTy - in - returnUs ([void_arg], - wrap_fn . Let (NonRec void_arg (Var realWorldPrimId)), - work_fn) - else - returnUs (work_args, wrap_fn, work_fn) - +---------------------- +mkWWstr [] + = returnUs ([], nop_fn, nop_fn) +mkWWstr (arg : args) + = mkWWstr_one arg `thenUs` \ (args1, wrap_fn1, work_fn1) -> + mkWWstr args `thenUs` \ (args2, wrap_fn2, work_fn2) -> + returnUs (args1 ++ args2, wrap_fn1 . wrap_fn2, work_fn1 . work_fn2) - -- Empty case -mk_ww [] - = returnUs ([], - \ wrapper_body -> wrapper_body, - \ worker_body -> worker_body) +---------------------- +-- mkWWstr_one wrap_arg = (work_args, wrap_fn, work_fn) +-- * wrap_fn assumes wrap_arg is in scope, +-- brings into scope work_args (via cases) +-- * work_fn assumes work_args are in scope, a +-- brings into scope wrap_arg (via lets) -mk_ww (arg : ds) - = case getIdDemandInfo arg of +mkWWstr_one arg + | isTyVar arg + = returnUs ([arg], nop_fn, nop_fn) - -- Absent case - WwLazy True -> - mk_ww ds `thenUs` \ (worker_args, wrap_fn, work_fn) -> - returnUs (worker_args, wrap_fn, mk_absent_let arg . work_fn) + | otherwise + = case idNewDemandInfo arg of - -- Unpack case - WwUnpack new_or_data True cs -> - getUniquesUs (length inst_con_arg_tys) `thenUs` \ uniqs -> - let - unpk_args = zipWith mk_ww_local uniqs inst_con_arg_tys - unpk_args_w_ds = zipWithEqual "mk_ww" setIdDemandInfo unpk_args cs - in - mk_ww (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 - inst_con_arg_tys = dataConArgTys data_con tycon_arg_tys - (arg_tycon, tycon_arg_tys, data_con) - = case (splitAlgTyConApp_maybe (idType arg)) of - - Just (arg_tycon, tycon_arg_tys, [data_con]) -> - -- The main event: a single-constructor data type - (arg_tycon, tycon_arg_tys, data_con) - - Just (_, _, data_cons) -> - pprPanic "mk_ww_arg_processing:" - (text "not one constr (interface files not consistent/up to date?)" - $$ (ppr arg <+> ppr (idType arg))) - - Nothing -> - panic "mk_ww_arg_processing: not datatype" + -- 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)) -> + returnUs ([], nop_fn, mk_absent_let arg) + -- Unpack case + Eval (Prod 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 "mkWWstr" set_worker_arg_info unpk_args cs + unbox_fn = mk_unpk_case arg unpk_args data_con arg_tycon + rebox_fn = Let (NonRec arg con_app) + con_app = mkConApp data_con (map Type tycon_arg_tys ++ map Var unpk_args) + in + mkWWstr unpk_args_w_ds `thenUs` \ (worker_args, wrap_fn, work_fn) -> + returnUs (worker_args, unbox_fn . wrap_fn, work_fn . rebox_fn) + -- Don't pass the arg, rebox instead + + -- `seq` demand; evaluate in wrapper in the hope + -- of dropping seqs in the worker + Eval (Poly Abs) + -> let + arg_w_unf = arg `setIdUnfolding` mkOtherCon [] + -- Tell the worker arg that it's sure to be evaluated + -- so that internal seqs can be dropped + in + returnUs ([arg_w_unf], mk_seq_case arg, nop_fn) + -- Pass the arg, anyway, even if it is in theory discarded + -- Consider + -- f x y = x `seq` y + -- x gets a (Eval (Poly Abs)) demand, but if we fail to pass it to the worker + -- we ABSOLUTELY MUST record that x is evaluated in the wrapper. + -- Something like: + -- f x y = x `seq` fw y + -- fw y = let x{Evald} = error "oops" in (x `seq` y) + -- If we don't pin on the "Evald" flag, the seq doesn't disappear, and + -- we end up evaluating the absent thunk. + -- But the Evald flag is pretty weird, and I worry that it might disappear + -- during simplification, so for now I've just nuked this whole case + -- Other cases - other_demand -> - mk_ww ds `thenUs` \ (worker_args, wrap_fn, work_fn) -> - returnUs (arg : worker_args, wrap_fn, work_fn) + other_demand -> returnUs ([arg], nop_fn, nop_fn) + + where + -- 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 (setIdNewDemandInfo worker_arg demand) + + set_one_shot | isOneShotLambda arg = setOneShotLambda + | otherwise = \x -> x \end{code} @@ -437,162 +408,67 @@ 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 + CoreExpr -> CoreExpr, -- New worker + Type) -- Type of worker's body -mkWWcpr body_ty NoCPRInfo - = returnUs (id, id) -- Must be just the strictness transf. -mkWWcpr body_ty (CPRInfo cpr_args) - = getUniqueUs `thenUs` \ body_arg_uniq -> - let - body_var = mk_ww_local body_arg_uniq body_ty - in - cpr_reconstruct body_ty cpr_info' `thenUs` \reconst_fn -> - cpr_flatten body_ty cpr_info' `thenUs` \flatten_fn -> - returnUs (reconst_fn, flatten_fn) - where - -- We only make use of the outer level of CprInfo, otherwise we - -- may lose laziness. :-( Hopefully, we will find a use for the - -- extra info some day (e.g. creating versions specialized to - -- the use made of the components of the result by the callee) - cpr_info' = CPRInfo (map (const NoCPRInfo) cpr_args) -\end{code} - - -@cpr_flatten@ takes the result type produced by the body and the info -from the CPR analysis and flattens the constructed product components. -These are returned in an unboxed tuple. +mkWWcpr body_ty RetCPR + | not (isAlgType body_ty) + = WARN( True, text "mkWWcpr: non-algebraic body type" <+> ppr body_ty ) + returnUs (id, id, body_ty) -\begin{code} -cpr_flatten :: Type -> CprInfo -> UniqSM (CoreExpr -> CoreExpr) -cpr_flatten ty cpr_info - = mk_cpr_case (ty, cpr_info) `thenUs` \(res_id, tup_ids, flatten_exp) -> - returnUs (\body -> Case body res_id - [(DEFAULT, [], flatten_exp (fst $ mk_unboxed_tuple tup_ids))]) - - - -mk_cpr_case :: (Type, CprInfo) -> - UniqSM (CoreBndr, -- Name of binder for this part of result - [(CoreExpr, Type)], -- expressions for flattened result - CoreExpr -> CoreExpr) -- add in code to flatten result - -mk_cpr_case (ty, NoCPRInfo) - -- this component must be returned as a component of the unboxed tuple result - = getUniqueUs `thenUs` \id_uniq -> - let id_id = mk_ww_local id_uniq ty in - returnUs (id_id, [(Var id_id, ty)], id) -mk_cpr_case (ty, cpr_info@(CPRInfo ci_args)) - | isNewTyCon tycon -- a new type: under the coercions must be a - -- constructed product - = ASSERT ( null $ tail inst_con_arg_tys ) - mk_cpr_case (target_of_from_type, cpr_info) - `thenUs` \(arg, tup, exp) -> - getUniqueUs `thenUs` \id_uniq -> - let id_id = mk_ww_local id_uniq ty - new_exp_case = \var -> Case (Note (Coerce (idType arg) ty) (Var id_id)) - arg - [(DEFAULT,[], exp var)] - in - returnUs (id_id, tup, new_exp_case) - - | otherwise -- a data type - -- flatten components - = mapUs mk_cpr_case (zip inst_con_arg_tys ci_args) - `thenUs` \sub_builds -> - getUniqueUs `thenUs` \id_uniq -> - let id_id = mk_ww_local id_uniq ty - (args, tup, exp) = unzip3 sub_builds - con_app = mkConApp data_con (map Var args) - new_tup = concat tup - new_exp_case = \var -> Case (Var id_id) (mkWildId ty) - [(DataCon data_con, args, - foldl (\e f -> f e) var exp)] - in - returnUs (id_id, new_tup, new_exp_case) - where - (data_con, tycon, tycon_arg_tys, inst_con_arg_tys) = splitType "mk_cpr_case" ty - from_type = head inst_con_arg_tys - -- if coerced from a function 'look through' to find result type - target_of_from_type = (snd.splitFunTys.snd.splitForAllTys) from_type - -\end{code} - -@cpr_reconstruct@ does the opposite of @cpr_flatten@. It takes the unboxed -tuple produced by the worker and reconstructs the structured result. - -\begin{code} -cpr_reconstruct :: Type -> CprInfo -> UniqSM (CoreExpr -> CoreExpr) -cpr_reconstruct ty cpr_info - = mk_cpr_let (ty,cpr_info) `thenUs` \(res_id, tup_ids, reconstruct_exp) -> - returnUs (\worker -> Case worker (mkWildId $ worker_type tup_ids) - [(DataCon $ unboxedTupleCon $ length tup_ids, - tup_ids, reconstruct_exp $ Var res_id)]) - - where - worker_type ids = mkTyConApp (unboxedTupleTyCon (length ids)) (map idType ids) - - -mk_cpr_let :: (Type, CprInfo) -> - UniqSM (CoreBndr, -- Binder for this component of result - [CoreBndr], -- Binders which will appear in worker's result - CoreExpr -> CoreExpr) -- Code to produce structured result. -mk_cpr_let (ty, NoCPRInfo) - -- this component will appear explicitly in the unboxed tuple. - = getUniqueUs `thenUs` \id_uniq -> + | n_con_args == 1 && isUnLiftedType con_arg_ty1 + -- Special case when there is a single result of unlifted type + -- + -- Wrapper: case (..call worker..) of x -> C x + -- Worker: case ( ..body.. ) of C x -> x + = getUniquesUs `thenUs` \ (work_uniq : arg_uniq : _) -> let - id_id = mk_ww_local id_uniq ty + work_wild = mk_ww_local work_uniq body_ty + arg = mk_ww_local arg_uniq con_arg_ty1 + con_app = mkConApp data_con (map Type tycon_arg_tys ++ [Var arg]) in - returnUs (id_id, [id_id], id) - -mk_cpr_let (ty, cpr_info@(CPRInfo ci_args)) - | isNewTyCon tycon -- a new type: must coerce the argument to this type - = ASSERT ( null $ tail inst_con_arg_tys ) - mk_cpr_let (target_of_from_type, cpr_info) - `thenUs` \(arg, tup, exp) -> - getUniqueUs `thenUs` \id_uniq -> - let id_id = mk_ww_local id_uniq ty - new_exp = \var -> exp (Let (NonRec id_id (Note (Coerce ty (idType arg)) (Var arg))) var) - in - returnUs (id_id, tup, new_exp) - - | otherwise -- a data type - -- reconstruct components then apply data con - = mapUs mk_cpr_let (zip inst_con_arg_tys ci_args) - `thenUs` \sub_builds -> - getUniqueUs `thenUs` \id_uniq -> - let id_id = mk_ww_local id_uniq ty - (args, tup, exp) = unzip3 sub_builds - con_app = mkConApp data_con $ (map Type tycon_arg_tys) ++ (map Var args) - new_tup = concat tup - new_exp = \var -> foldl (\e f -> f e) (Let (NonRec id_id con_app) var) exp + returnUs (\ wkr_call -> Case wkr_call arg [(DEFAULT, [], con_app)], + \ body -> workerCase body work_wild [(DataAlt data_con, [arg], Var arg)], + con_arg_ty1) + + | otherwise -- The general case + -- Wrapper: case (..call worker..) of (# a, b #) -> C a b + -- Worker: case ( ...body... ) of C a b -> (# a, b #) + = getUniquesUs `thenUs` \ uniqs -> + let + (wrap_wild : work_wild : args) = zipWith mk_ww_local uniqs (ubx_tup_ty : body_ty : con_arg_tys) + arg_vars = map Var args + ubx_tup_con = tupleCon Unboxed n_con_args + ubx_tup_ty = exprType ubx_tup_app + ubx_tup_app = mkConApp ubx_tup_con (map Type con_arg_tys ++ arg_vars) + con_app = mkConApp data_con (map Type tycon_arg_tys ++ arg_vars) in - returnUs (id_id, new_tup, new_exp) + returnUs (\ wkr_call -> Case wkr_call wrap_wild [(DataAlt ubx_tup_con, args, con_app)], + \ body -> workerCase body work_wild [(DataAlt data_con, args, ubx_tup_app)], + ubx_tup_ty) where - (data_con, tycon, tycon_arg_tys, inst_con_arg_tys) = splitType "mk_cpr_let" ty - from_type = head inst_con_arg_tys - -- if coerced from a function 'look through' to find result type - target_of_from_type = (snd.splitFunTys.snd.splitForAllTys) from_type - - -splitType :: String -> Type -> (DataCon, TyCon, [Type], [Type]) -splitType fname ty = (data_con, tycon, tycon_arg_tys, dataConArgTys data_con tycon_arg_tys) - where - (data_con, tycon, tycon_arg_tys) - = case (splitAlgTyConApp_maybe ty) of - Just (arg_tycon, tycon_arg_tys, [data_con]) -> - -- The main event: a single-constructor data type - (data_con, arg_tycon, tycon_arg_tys) - - Just (_, _, data_cons) -> - pprPanic (fname ++ ":") - (text "not one constr (interface files not consistent/up to date?)" - $$ ppr ty) - - Nothing -> - pprPanic (fname ++ ":") - (text "not a datatype" $$ ppr ty) + (_, tycon_arg_tys, data_con, con_arg_tys) = splitProductType "mkWWcpr" body_ty + 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 +-- +-- then we want the CPR'd worker to look like +-- \ x -> _scc_ "foo" (case E of I# x -> x) +-- and definitely not +-- \ x -> case (_scc_ "foo" E) of I# x -> x) +-- +-- This transform doesn't move work or allocation +-- from one cost centre to another + +workerCase (Note (SCC cc) e) arg alts = Note (SCC cc) (Case e arg alts) +workerCase e arg alts = Case e arg alts \end{code} @@ -606,26 +482,21 @@ splitType fname ty = (data_con, tycon, tycon_arg_tys, dataConArgTys data_con tyc \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 = mkRuntimeErrorApp rUNTIME_ERROR_ID arg_ty 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) - [(DataCon boxing_con, unpk_args, body)] + [(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 @@ -638,26 +509,5 @@ 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 - = Let (NonRec arg (Con (DataCon 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 - - -mk_unboxed_tuple :: [(CoreExpr, Type)] -> (CoreExpr, Type) -mk_unboxed_tuple contents - = (mkConApp (unboxedTupleCon (length contents)) - (map (Type . snd) contents ++ - map fst contents), - mkTyConApp (unboxedTupleTyCon (length contents)) - (map snd contents)) +mk_ww_local uniq ty = mkSysLocal FSLIT("ww") uniq ty \end{code}