X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Fstranal%2FWwLib.lhs;h=54a167ddcbf7bb741cb09a6c7c5dfc3a54d06bbe;hb=e7c3f957fd36fd9f6369183b7a31e2a4a4c21b43;hp=b87bd4c61c3b5e3805fe9bc22606524e6b9729dd;hpb=6c381e873e222417d9a67aeec77b9555eca7b7a8;p=ghc-hetmet.git diff --git a/ghc/compiler/stranal/WwLib.lhs b/ghc/compiler/stranal/WwLib.lhs index b87bd4c..54a167d 100644 --- a/ghc/compiler/stranal/WwLib.lhs +++ b/ghc/compiler/stranal/WwLib.lhs @@ -1,72 +1,35 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1993-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1993-1998 % \section[WwLib]{A library for the ``worker/wrapper'' back-end to the strictness analyser} \begin{code} -#include "HsVersions.h" - -module WwLib ( - WwBinding(..), - - mkWwBodies, mAX_WORKER_ARGS, +module WwLib ( mkWwBodies, mkWWstr, mkWorkerArgs ) where - -- our friendly worker/wrapper monad: - WwM(..), - returnWw, thenWw, mapWw, - getUniqueWw, uniqSMtoWwM - - -- and to make the interface self-sufficient... - ) where - -import Ubiq{-uitous-} +#include "HsVersions.h" -import PrelInfo ( aBSENT_ERROR_ID ) -{- -import Id ( mkWorkerId, mkSysLocal, idType, - getInstantiatedDataConSig, getIdInfo, - replaceIdInfo, addIdStrictness, DataCon(..) +import CoreSyn +import CoreUtils ( exprType ) +import Id ( Id, idType, mkSysLocal, idNewDemandInfo, setIdNewDemandInfo, + isOneShotLambda, setOneShotLambda, setIdUnfolding, + setIdInfo ) -import IdInfo -- lots of things -import Maybes ( maybeToBool, Maybe(..), MaybeErr ) -import SaLib -import SrcLoc ( mkUnknownSrcLoc ) -import Type ( mkTyVarTy, mkFunTys, isPrimType, - maybeDataTyCon, quantifyTy +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 UniqSupply --} -import Util ( panic ) - -infixr 9 `thenWw` - -quantifyTy = panic "WwLib.quantifyTy" +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 [CoreBinding] - | 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} %************************************************************************ %* * @@ -74,54 +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 @@ -138,13 +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 @@ -154,12 +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. @@ -170,291 +89,426 @@ probably slightly paranoid, but OK in practice.) If it isn't the same, we ``revise'' the strictness info, so that we won't propagate the unusable strictness-info into the interfaces. -========================== -Here's the real fun... The wrapper's ``deconstructing'' of arguments -and the worker's putting them back together again are ``duals'' in -some sense. - -What we do is walk along the @Demand@ list, producing two -expressions (one for wrapper, one for worker...), each with a ``hole'' -in it, where we will later plug in more information. For our previous -example, the expressions-with-HOLES are: -\begin{verbatim} -\ x ys -> -- wrapper - case x of - I# x# -> <> x# ys +%************************************************************************ +%* * +\subsection{The worker wrapper core} +%* * +%************************************************************************ -\ x# ys -> -- worker - let - x = I# x# - in - <> -\end{verbatim} -(Actually, we add the lambda-bound arguments at the end...) (The big -Lambdas are added on the front later.) +@mkWwBodies@ is called when doing the worker/wrapper split inside a module. \begin{code} -mkWwBodies - :: Type -- Type of the *body* of the orig - -- function; i.e. /\ tyvars -> \ vars -> body - -> [TyVar] -- Type lambda vars of original function - -> [Id] -- Args of original function - -> [Demand] -- Strictness info for those args - - -> UniqSM (Maybe -- Nothing iff (a) no interesting split possible - -- (b) any unpack on abstract type - (Id -> CoreExpr, -- Wrapper expr w/ - -- hole for worker id - CoreExpr -> CoreExpr, -- Worker expr w/ hole - -- for original fn body - StrictnessInfo, -- Worker strictness info - Type -> Type) -- Worker type w/ hole - ) -- for type of original fn body - - -mkWwBodies body_ty tyvars args arg_infos - = ASSERT(length args == length arg_infos) - -- or you can get disastrous user/definer-module mismatches - if (all_absent_args_and_unboxed_value body_ty arg_infos) - then returnUs Nothing - - else -- the rest... - mk_ww_arg_processing args arg_infos (mAX_WORKER_ARGS - nonAbsentArgs arg_infos) - `thenUsMaybe` \ (wrap_frag, work_args_info, work_frag) -> +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_args, wrkr_demands) = unzip work_args_info + (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 + one_shots' = one_shots ++ repeat False +\end{code} - wrkr_strictness = mkStrictnessInfo wrkr_demands Nothing -- no worker-of-worker... - wrapper_w_hole = \ worker_id -> - mkLam tyvars args ( - wrap_frag ( - mkCoTyApps (Var worker_id) (map mkTyVarTy tyvars) - )) +%************************************************************************ +%* * +\subsection{Making wrapper args} +%* * +%************************************************************************ - worker_w_hole = \ orig_body -> - mkLam tyvars work_args ( - work_frag orig_body - ) +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. - worker_ty_w_hole = \ body_ty -> - snd (quantifyTy tyvars ( - mkFunTys (map idType work_args) body_ty - )) - in - returnUs (Just (wrapper_w_hole, worker_w_hole, wrkr_strictness, worker_ty_w_hole)) - where - -- "all_absent_args_and_unboxed_value": - -- check for the obscure case of "\ x y z ... -> body" where - -- (a) *all* of the args x, y, z,... are absent, and - -- (b) the type of body is unboxed - -- If these conditions are true, we must *not* play worker/wrapper games! - - all_absent_args_and_unboxed_value body_ty arg_infos - = not (null arg_infos) - && all is_absent_arg arg_infos - && isPrimType body_ty - - is_absent_arg (WwLazy True) = True - is_absent_arg _ = False + 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 + +We use the state-token type which generates no code. + +\begin{code} +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} -Important: mk_ww_arg_processing doesn't check -for an "interesting" split. It just races ahead and makes the -split, even if there's no unpacking at all. This is important for -when it calls itself recursively. -It returns Nothing only if it encounters an abstract type in mid-flight. +%************************************************************************ +%* * +\subsection{Coercion stuff} +%* * +%************************************************************************ + + +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} -mAX_WORKER_ARGS :: Int -- ToDo: set via flag -mAX_WORKER_ARGS = 6 -- Hmm... but this is an everything-must- - -- be-compiled-with-the-same-val thing... - -mk_ww_arg_processing - :: [Id] -- Args of original function - -> [Demand] -- Strictness info for those args - -- must be at least as long as args - - -> Int -- Number of extra args we are prepared to add. - -- This prevents over-eager unpacking, leading - -- to huge-arity functions. - - -> UniqSM (Maybe -- Nothing iff any unpack on abstract type - (CoreExpr -> CoreExpr, -- Wrapper expr w/ - -- hole for worker id - -- applied to types - [(Id,Demand)], -- Worker's args - -- and their strictness info - CoreExpr -> CoreExpr) -- Worker body expr w/ hole - ) -- for original fn body - -mk_ww_arg_processing [] _ _ = returnUs (Just (id, [], id)) - -mk_ww_arg_processing (arg : args) (WwLazy True : infos) max_extra_args - = -- Absent argument - -- So, finish args to the right... - --pprTrace "Absent; num_wrkr_args=" (ppInt num_wrkr_args) ( +-- 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 - arg_ty = idType arg + (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 - mk_ww_arg_processing args infos max_extra_args - -- we've already discounted for absent args, - -- so we don't change max_extra_args - `thenUsMaybe` \ (wrap_rest, work_args_info, work_rest) -> - - -- wrapper doesn't pass this arg to worker: - returnUs (Just ( - -- wrapper: - \ hole -> wrap_rest hole, - - -- worker: - work_args_info, -- NB: no argument added - \ hole -> mk_absent_let arg arg_ty (work_rest hole) - )) - --) - where - mk_absent_let arg arg_ty body - = if not (isPrimType arg_ty) then - Let (NonRec arg (mkCoTyApp (Var aBSENT_ERROR_ID) arg_ty)) body - else -- quite horrible - panic "WwLib: haven't done mk_absent_let for primitives yet" - - -mk_ww_arg_processing (arg : args) (WwUnpack cmpnt_infos : infos) max_extra_args - | new_max_extra_args > 0 -- Check that we are prepared to add arguments - = -- this is the complicated one. - --pprTrace "Unpack; num_wrkr_args=" (ppCat [ppInt num_wrkr_args, ppStr "; new_max=", ppInt new_num_wrkr_args, ppStr "; arg=", ppr PprDebug arg, ppr PprDebug (WwUnpack cmpnt_infos)]) ( - case maybeDataTyCon arg_ty of - - Nothing -> -- Not a data type - panic "mk_ww_arg_processing: not datatype" - - Just (_, _, []) -> -- An abstract type - -- We have to give up on the whole idea - returnUs Nothing - Just (_, _, (_:_:_)) -> -- Two or more constructors; that's odd - panic "mk_ww_arg_processing: multi-constr" - - Just (arg_tycon, tycon_arg_tys, [data_con]) -> - -- The main event: a single-constructor data type - - let - (_,inst_con_arg_tys,_) - = getInstantiatedDataConSig data_con tycon_arg_tys - in - getUniques (length inst_con_arg_tys) `thenUs` \ uniqs -> - - let - unpk_args = zipWithEqual - (\ u t -> mkSysLocal SLIT("upk") u t mkUnknownSrcLoc) - uniqs inst_con_arg_tys - in - -- In processing the rest, push the sub-component args - -- and infos on the front of the current bunch - mk_ww_arg_processing (unpk_args ++ args) (cmpnt_infos ++ infos) new_max_extra_args - `thenUsMaybe` \ (wrap_rest, work_args_info, work_rest) -> - - returnUs (Just ( - -- wrapper: unpack the value - \ hole -> mk_unpk_case arg unpk_args - data_con arg_tycon - (wrap_rest hole), - - -- worker: expect the unpacked value; - -- reconstruct the orig value with a "let" - work_args_info, - \ hole -> work_rest (mk_pk_let arg data_con tycon_arg_tys unpk_args hole) - )) - --) +{- 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 + = 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 - arg_ty = idType arg + set_one_shot True id = setOneShotLambda id + set_one_shot False id = id +\end{code} - new_max_extra_args - = max_extra_args - + 1 -- We won't pass the original arg now - - nonAbsentArgs cmpnt_infos -- But we will pass an arg for each cmpt - mk_unpk_case arg unpk_args boxing_con boxing_tycon body - = Case (Var arg) ( - AlgAlts [(boxing_con, unpk_args, body)] - NoDefault - ) +%************************************************************************ +%* * +\subsection{Strictness stuff} +%* * +%************************************************************************ - mk_pk_let arg boxing_con con_tys unpk_args body - = Let (NonRec arg (Con boxing_con con_tys [VarArg a | a <- unpk_args])) - body +\begin{code} +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 + -- This fn adds the unboxing + + CoreExpr -> CoreExpr) -- Worker body, lacking the original body of the function, + -- and lacking its lambdas. + -- This fn does the reboxing + +---------------------- +nop_fn body = body + +---------------------- +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) + + +---------------------- +-- 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) + +mkWWstr_one arg + | isTyVar arg + = returnUs ([arg], nop_fn, nop_fn) -mk_ww_arg_processing (arg : args) (arg_demand : infos) max_extra_args | otherwise - = -- For all others at the moment, we just - -- pass them to the worker unchanged. - --pprTrace "Other; num_wrkr_args=" (ppCat [ppInt num_wrkr_args, ppStr ";arg=", ppr PprDebug arg, ppr PprDebug arg_demand]) ( - - -- Finish args to the right... - mk_ww_arg_processing args infos max_extra_args - `thenUsMaybe` \ (wrap_rest, work_args_info, work_rest) -> - - returnUs (Just ( - -- wrapper: - \ hole -> wrap_rest (App hole (VarArg arg)), - - -- worker: - (arg, arg_demand) : work_args_info, - \ hole -> work_rest hole - )) - --) + = case idNewDemandInfo arg of + + -- 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` evaldUnfolding + -- 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 -> 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} + %************************************************************************ %* * -\subsection[monad-WwLib]{Simple monad for worker/wrapper} +\subsection{CPR stuff} %* * %************************************************************************ -In this monad, we thread a @UniqueSupply@, and we carry a -@GlobalSwitch@-lookup function downwards. + +@mkWWcpr@ takes the worker/wrapper pair produced from the strictness +info and adds in the CPR transformation. The worker returns an +unboxed tuple containing non-CPR components. The wrapper takes this +tuple and re-produces the correct structured output. + +The non-CPR results appear ordered in the unboxed tuple as if by a +left-to-right traversal of the result structure. + \begin{code} -type WwM result - = UniqSupply - -> (GlobalSwitch -> Bool) - -> result - -{-# INLINE thenWw #-} -{-# INLINE returnWw #-} - -returnWw :: a -> WwM a -thenWw :: WwM a -> (a -> WwM b) -> WwM b -mapWw :: (a -> WwM b) -> [a] -> WwM [b] - -returnWw expr ns sw = expr - -thenWw m k us sw_chk - = case splitUniqSupply us of { (s1, s2) -> - case (m s1 sw_chk) of { m_res -> - k m_res s2 sw_chk }} - -mapWw f [] = returnWw [] -mapWw f (x:xs) - = f x `thenWw` \ x' -> - mapWw f xs `thenWw` \ xs' -> - returnWw (x':xs') +mkWWcpr :: Type -- function body type + -> DmdResult -- CPR analysis results + -> UniqSM (CoreExpr -> CoreExpr, -- New wrapper + CoreExpr -> CoreExpr, -- New worker + Type) -- Type of worker's body + +mkWWcpr body_ty RetCPR + | not (isAlgType body_ty) + = WARN( True, text "mkWWcpr: non-algebraic body type" <+> ppr body_ty ) + returnUs (id, id, body_ty) + + | 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 + 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 (\ wkr_call -> Case wkr_call arg (exprType con_app) [(DEFAULT, [], con_app)], + \ body -> workerCase body work_wild con_arg_ty1 [(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 (\ wkr_call -> Case wkr_call wrap_wild (exprType con_app) [(DataAlt ubx_tup_con, args, con_app)], + \ body -> workerCase body work_wild ubx_tup_ty [(DataAlt data_con, args, ubx_tup_app)], + ubx_tup_ty) + where + (_, 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 ty alts = Note (SCC cc) (Case e arg ty alts) +workerCase e arg ty alts = Case e arg ty alts \end{code} -\begin{code} -getUniqueWw :: WwM Unique -uniqSMtoWwM :: UniqSM a -> WwM a -getUniqueWw us sw_chk = getUnique us +%************************************************************************ +%* * +\subsection{Utilities} +%* * +%************************************************************************ -uniqSMtoWwM u_obj us sw_chk = u_obj us -thenUsMaybe :: UniqSM (Maybe a) -> (a -> UniqSM (Maybe b)) -> UniqSM (Maybe b) -thenUsMaybe m k - = m `thenUs` \ result -> - case result of - Nothing -> returnUs Nothing - Just x -> k x +\begin{code} +mk_absent_let arg body + | not (isUnLiftedType arg_ty) + = 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 arg unpk_args boxing_con boxing_tycon body + -- A data type + = Case (Var arg) + (sanitiseCaseBndr arg) + (exprType body) + [(DataAlt boxing_con, unpk_args, body)] + +mk_seq_case arg body = Case (Var arg) (sanitiseCaseBndr arg) (exprType body) [(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. +-- But we *must* throw away all its IdInfo. In particular, the argument +-- will have demand info on it, and that demand info may be incorrect for +-- the case binder. e.g. case ww_arg of ww_arg { I# x -> ... } +-- Quite likely ww_arg isn't used in '...'. The case may get discarded +-- if the case binder says "I'm demanded". This happened in a situation +-- like (x+y) `seq` .... +sanitiseCaseBndr id = id `setIdInfo` vanillaIdInfo + +mk_ww_local uniq ty = mkSysLocal FSLIT("ww") uniq ty \end{code}