X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Fstranal%2FWorkWrap.lhs;h=e556ead4fe5c8c6435e5dbcf2319e15accd5944f;hb=dbb27b50948726c09fae681bca921ba3c00d859b;hp=e433e94346f5408e272f3ab62230a8f9c90e37ba;hpb=26741ec416bae2c502ef00a2ba0e79050a32cb67;p=ghc-hetmet.git diff --git a/ghc/compiler/stranal/WorkWrap.lhs b/ghc/compiler/stranal/WorkWrap.lhs index e433e94..e556ead 100644 --- a/ghc/compiler/stranal/WorkWrap.lhs +++ b/ghc/compiler/stranal/WorkWrap.lhs @@ -1,58 +1,89 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1993-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1993-1998 % \section[WorkWrap]{Worker/wrapper-generating back-end of strictness analyser} \begin{code} -#include "HsVersions.h" - -module WorkWrap ( workersAndWrappers ) where +module WorkWrap ( wwTopBinds, mkWrapper ) where -IMP_Ubiq(){-uitous-} +#include "HsVersions.h" import CoreSyn -import CoreUnfold ( UnfoldingGuidance(..) ) -import CoreUtils ( coreExprType ) -import Id ( idWantsToBeINLINEd, getIdStrictness, mkWorkerId, - getIdInfo, GenId +import CoreUnfold ( Unfolding, certainlyWillInline ) +import CoreLint ( beginPass, endPass ) +import CoreUtils ( exprType, exprEtaExpandArity ) +import MkId ( mkWorkerId ) +import Id ( Id, idType, idStrictness, idArity, isOneShotLambda, + setIdStrictness, idInlinePragma, + setIdWorkerInfo, idCprInfo, setInlinePragma ) +import Type ( Type, isNewType, splitForAllTys, splitFunTys ) +import IdInfo ( mkStrictnessInfo, noStrictnessInfo, StrictnessInfo(..), + CprInfo(..), exactArity, InlinePragInfo(..), isNeverInlinePrag, + WorkerInfo(..) ) -import IdInfo ( noIdInfo, addInfo_UF, indicatesWorker, - mkStrictnessInfo, StrictnessInfo(..) - ) -import SaLib -import UniqSupply ( returnUs, thenUs, mapUs, getUnique, SYN_IE(UniqSM) ) +import Demand ( Demand, wwLazy ) +import UniqSupply ( UniqSupply, initUs_, returnUs, thenUs, mapUs, getUniqueUs, UniqSM ) +import CmdLineOpts import WwLib -import Util ( panic{-ToDo:rm-} ) - -replaceIdInfo = panic "WorkWrap.replaceIdInfo (ToDo)" -iWantToBeINLINEd = panic "WorkWrap.iWantToBeINLINEd (ToDo)" +import Outputable \end{code} -We take Core bindings whose binders have their strictness attached (by -the front-end of the strictness analyser), and we return some -``plain'' bindings which have been worker/wrapper-ified, meaning: +We take Core bindings whose binders have: + \begin{enumerate} -\item -Functions have been split into workers and wrappers where appropriate; -\item -Binders' @IdInfos@ have been updated to reflect the existence -of these workers/wrappers (this is where we get STRICTNESS pragma + +\item Strictness attached (by the front-end of the strictness +analyser), and / or + +\item Constructed Product Result information attached by the CPR +analysis pass. + +\end{enumerate} + +and we return some ``plain'' bindings which have been +worker/wrapper-ified, meaning: + +\begin{enumerate} + +\item Functions have been split into workers and wrappers where +appropriate. If a function has both strictness and CPR properties +then only one worker/wrapper doing both transformations is produced; + +\item Binders' @IdInfos@ have been updated to reflect the existence of +these workers/wrappers (this is where we get STRICTNESS and CPR pragma info for exported values). \end{enumerate} \begin{code} -workersAndWrappers :: [CoreBinding] -> UniqSM [CoreBinding] -workersAndWrappers top_binds - = mapUs (wwBind True{-top-level-}) top_binds `thenUs` \ top_binds2 -> - let - top_binds3 = map make_top_binding top_binds2 - in - returnUs (concat top_binds3) - where - make_top_binding :: WwBinding -> [CoreBinding] +wwTopBinds :: DynFlags + -> UniqSupply + -> [CoreBind] + -> IO [CoreBind] + +wwTopBinds dflags us binds + = do { + beginPass dflags "Worker Wrapper binds"; + + -- Create worker/wrappers, and mark binders with their + -- "strictness info" [which encodes their worker/wrapper-ness] + let { binds' = workersAndWrappers us binds }; + + endPass dflags "Worker Wrapper binds" + (dopt Opt_D_dump_worker_wrapper dflags || + dopt Opt_D_verbose_core2core dflags) + binds' + } +\end{code} + + +\begin{code} +workersAndWrappers :: UniqSupply -> [CoreBind] -> [CoreBind] - make_top_binding (WwLet binds) = binds +workersAndWrappers us top_binds + = initUs_ us $ + mapUs wwBind top_binds `thenUs` \ top_binds' -> + returnUs (concat top_binds') \end{code} %************************************************************************ @@ -65,42 +96,39 @@ workersAndWrappers top_binds turn. Non-recursive case first, then recursive... \begin{code} -wwBind :: Bool -- True <=> top-level binding - -> CoreBinding - -> UniqSM WwBinding -- returns a WwBinding intermediate form; +wwBind :: CoreBind + -> UniqSM [CoreBind] -- returns a WwBinding intermediate form; -- the caller will convert to Expr/Binding, -- as appropriate. -wwBind top_level (NonRec binder rhs) - = wwExpr rhs `thenUs` \ new_rhs -> - tryWW binder new_rhs `thenUs` \ new_pairs -> - returnUs (WwLet [NonRec b e | (b,e) <- new_pairs]) +wwBind (NonRec binder rhs) + = wwExpr rhs `thenUs` \ new_rhs -> + tryWW True {- non-recursive -} binder new_rhs `thenUs` \ new_pairs -> + returnUs [NonRec b e | (b,e) <- new_pairs] -- Generated bindings must be non-recursive -- because the original binding was. ------------------------------ -wwBind top_level (Rec pairs) +wwBind (Rec pairs) = mapUs do_one pairs `thenUs` \ new_pairs -> - returnUs (WwLet [Rec (concat new_pairs)]) + returnUs [Rec (concat new_pairs)] where do_one (binder, rhs) = wwExpr rhs `thenUs` \ new_rhs -> - tryWW binder new_rhs + tryWW False {- recursive -} binder new_rhs \end{code} @wwExpr@ basically just walks the tree, looking for appropriate annotations that can be used. Remember it is @wwBind@ that does the matching by looking for strict arguments of the correct type. @wwExpr@ is a version that just returns the ``Plain'' Tree. -???????????????? ToDo \begin{code} wwExpr :: CoreExpr -> UniqSM CoreExpr +wwExpr e@(Type _) = returnUs e wwExpr e@(Var _) = returnUs e wwExpr e@(Lit _) = returnUs e -wwExpr e@(Con _ _) = returnUs e -wwExpr e@(Prim _ _) = returnUs e wwExpr (Lam binder expr) = wwExpr expr `thenUs` \ new_expr -> @@ -108,53 +136,26 @@ wwExpr (Lam binder expr) wwExpr (App f a) = wwExpr f `thenUs` \ new_f -> - returnUs (App new_f a) + wwExpr a `thenUs` \ new_a -> + returnUs (App new_f new_a) -wwExpr (SCC cc expr) +wwExpr (Note note expr) = wwExpr expr `thenUs` \ new_expr -> - returnUs (SCC cc new_expr) - -wwExpr (Coerce c ty expr) - = wwExpr expr `thenUs` \ new_expr -> - returnUs (Coerce c ty new_expr) + returnUs (Note note new_expr) wwExpr (Let bind expr) - = wwBind False{-not top-level-} bind `thenUs` \ intermediate_bind -> - wwExpr expr `thenUs` \ new_expr -> - returnUs (mash_ww_bind intermediate_bind new_expr) - where - mash_ww_bind (WwLet binds) body = mkCoLetsNoUnboxed binds body - mash_ww_bind (WwCase case_fn) body = case_fn body + = wwBind bind `thenUs` \ intermediate_bind -> + wwExpr expr `thenUs` \ new_expr -> + returnUs (mkLets intermediate_bind new_expr) -wwExpr (Case expr alts) +wwExpr (Case expr binder alts) = wwExpr expr `thenUs` \ new_expr -> - ww_alts alts `thenUs` \ new_alts -> - returnUs (Case new_expr new_alts) + mapUs ww_alt alts `thenUs` \ new_alts -> + returnUs (Case new_expr binder new_alts) where - ww_alts (AlgAlts alts deflt) - = mapUs ww_alg_alt alts `thenUs` \ new_alts -> - ww_deflt deflt `thenUs` \ new_deflt -> - returnUs (AlgAlts new_alts new_deflt) - - ww_alts (PrimAlts alts deflt) - = mapUs ww_prim_alt alts `thenUs` \ new_alts -> - ww_deflt deflt `thenUs` \ new_deflt -> - returnUs (PrimAlts new_alts new_deflt) - - ww_alg_alt (con, binders, rhs) + ww_alt (con, binders, rhs) = wwExpr rhs `thenUs` \ new_rhs -> returnUs (con, binders, new_rhs) - - ww_prim_alt (lit, rhs) - = wwExpr rhs `thenUs` \ new_rhs -> - returnUs (lit, new_rhs) - - ww_deflt NoDefault - = returnUs NoDefault - - ww_deflt (BindDefault binder rhs) - = wwExpr rhs `thenUs` \ new_rhs -> - returnUs (BindDefault binder new_rhs) \end{code} %************************************************************************ @@ -176,78 +177,173 @@ reason), then we don't w-w it. The only reason this is monadised is for the unique supply. \begin{code} -tryWW :: Id -- the fn binder - -> CoreExpr -- the bound rhs; its innards +tryWW :: Bool -- True <=> a non-recursive binding + -> Id -- The fn binder + -> CoreExpr -- The bound rhs; its innards -- are already ww'd -> UniqSM [(Id, CoreExpr)] -- either *one* or *two* pairs; -- if one, then no worker (only -- the orig "wrapper" lives on); -- if two, then a worker and a -- wrapper. -tryWW fn_id rhs - | idWantsToBeINLINEd fn_id - -- No point in worker/wrappering something that is going to be - -- INLINEd wholesale anyway. If the strictness analyser is run - -- twice, this test also prevents wrappers (which are INLINEd) - -- from being re-done. - = do_nothing - - | otherwise - = case (getIdStrictness fn_id) of - - NoStrictnessInfo -> do_nothing - BottomGuaranteed -> do_nothing - StrictnessInfo [] _ -> do_nothing -- V weird (but possible?) - - StrictnessInfo args_info _ -> - if not (indicatesWorker args_info) then - do_nothing - else - - -- OK, it looks as if a worker is worth a try - let - (uvars, tyvars, args, body) = collectBinders rhs - body_ty = coreExprType body - in - mkWwBodies body_ty tyvars args args_info `thenUs` \ result -> - case result of - - Nothing -> -- Very peculiar. This can only happen if we hit an - -- abstract type, which we shouldn't have since we've - -- constructed the args_info in this module! - - -- False. We might hit the all-args-absent-and-the- - -- body-is-unboxed case. A Nothing is legit. (WDP 94/10) - do_nothing - - Just (wrapper_w_hole, worker_w_hole, worker_strictness, worker_ty_w_hole) -> - - -- Terrific! It worked! - getUnique `thenUs` \ worker_uniq -> - let - worker_ty = worker_ty_w_hole body_ty - - worker_id = mkWorkerId worker_uniq fn_id worker_ty - (noIdInfo `addInfo` worker_strictness) - - wrapper_rhs = wrapper_w_hole worker_id - worker_rhs = worker_w_hole body - - revised_strictness_info - = -- We know the basic strictness info already, but - -- we need to slam in the exact identity of the - -- worker Id: - mkStrictnessInfo args_info (Just worker_id) - - wrapper_id = fn_id `replaceIdInfo` - (getIdInfo fn_id `addInfo` - revised_strictness_info `addInfo_UF` - iWantToBeINLINEd UnfoldAlways) - -- NB! the "iWantToBeINLINEd" part adds an INLINE pragma to - -- the wrapper, which is of course what we want. - in - returnUs [ (worker_id, worker_rhs), -- worker comes first - (wrapper_id, wrapper_rhs) ] -- because wrapper mentions it +tryWW non_rec fn_id rhs + | isNeverInlinePrag inline_prag || arity == 0 + = -- Don't split things that will never be inlined + returnUs [ (fn_id, rhs) ] + + | non_rec && not do_coerce_ww && certainlyWillInline fn_id + -- No point in worker/wrappering a function that is going to be + -- INLINEd wholesale anyway. If the strictness analyser is run + -- twice, this test also prevents wrappers (which are INLINEd) + -- from being re-done. + -- + -- The do_coerce_ww test is so that + -- a function with a coerce should w/w to get rid + -- of the coerces, which can significantly improve its arity. + -- Example: f []   = return [] :: IO [Int] + -- f (x:xs) = return (x:xs) + -- If we aren't careful we end up with + -- f = \ x -> case x of { + -- x:xs -> __coerce (IO [Int]) (\ s -> (# s, x:xs #) + -- [] -> lvl_sJ8 + -- + -- + -- OUT OF DATE NOTE, kept for info: + -- It's out of date because now wrappers look very cheap + -- even when they are inlined. + -- In this case we add an INLINE pragma to the RHS. Why? + -- Because consider + -- f = \x -> g x x + -- g = \yz -> ... -- And g is strict + -- Then f is small, so we don't w/w it. But g is big, and we do, so + -- g's wrapper will get inlined in f's RHS, which makes f look big now. + -- So f doesn't get inlined, but it is strict and we have failed to w/w it. + = returnUs [ (fn_id, rhs) ] + + | not (do_strict_ww || do_cpr_ww || do_coerce_ww) + = returnUs [ (fn_id, rhs) ] + + | otherwise -- Do w/w split + = mkWwBodies fun_ty arity wrap_dmds result_bot one_shots cpr_info `thenUs` \ (work_demands, wrap_fn, work_fn) -> + getUniqueUs `thenUs` \ work_uniq -> + let + work_rhs = work_fn rhs + proto_work_id = mkWorkerId work_uniq fn_id (exprType work_rhs) + `setInlinePragma` inline_prag + + work_id | has_strictness = proto_work_id `setIdStrictness` mkStrictnessInfo (work_demands, result_bot) + | otherwise = proto_work_id + + wrap_rhs = wrap_fn work_id + wrap_id = fn_id `setIdStrictness` wrapper_strictness + `setIdWorkerInfo` HasWorker work_id arity + `setInlinePragma` NoInlinePragInfo -- Put it on the worker instead + -- Add info to the wrapper: + -- (a) we want to set its arity + -- (b) we want to pin on its revised strictness info + -- (c) we pin on its worker id + in + returnUs ([(work_id, work_rhs), (wrap_id, wrap_rhs)]) + -- Worker first, because wrapper mentions it + -- mkWwBodies has already built a wrap_rhs with an INLINE pragma wrapped around it + where + fun_ty = idType fn_id + arity = idArity fn_id -- The arity is set by the simplifier using exprEtaExpandArity + -- So it may be more than the number of top-level-visible lambdas + + inline_prag = idInlinePragma fn_id + + strictness_info = idStrictness fn_id + has_strictness = case strictness_info of + StrictnessInfo _ _ -> True + NoStrictnessInfo -> False + (arg_demands, result_bot) = case strictness_info of + StrictnessInfo d r -> (d, r) + NoStrictnessInfo -> ([], False) + + wrap_dmds = setUnpackStrategy arg_demands + do_strict_ww = WARN( has_strictness && not result_bot && arity < length arg_demands && worthSplitting wrap_dmds result_bot, + text "Insufficient arity" <+> ppr fn_id <+> ppr arity <+> ppr arg_demands ) + (result_bot || arity >= length arg_demands) -- Only if there's enough visible arity + && -- (else strictness info isn't valid) + -- + worthSplitting wrap_dmds result_bot -- And it's useful + -- worthSplitting returns False for an empty list of demands, + -- and hence do_strict_ww is False if arity is zero + -- Also it's false if there is no strictness (arg_demands is []) + + wrapper_strictness | has_strictness = mkStrictnessInfo (wrap_dmds, result_bot) + | otherwise = noStrictnessInfo + + ------------------------------------------------------------- + cpr_info = idCprInfo fn_id + do_cpr_ww = arity > 0 && + case cpr_info of + ReturnsCPR -> True + other -> False + + ------------------------------------------------------------- + do_coerce_ww = check_for_coerce arity fun_ty + -- We are willing to do a w/w even if the arity is zero. + -- x = coerce t E + -- ==> + -- x' = E + -- x = coerce t x' + + ------------------------------------------------------------- + one_shots = get_one_shots rhs + +-- See if there's a Coerce before we run out of arity; +-- if so, it's worth trying a w/w split. Reason: we find +-- functions like f = coerce (\s -> e) +-- and g = \x -> coerce (\s -> e) +-- and they may have no useful strictness or cpr info, but if we +-- do the w/w thing we get rid of the coerces. + +check_for_coerce arity ty + = length arg_tys <= arity && isNewType res_ty + -- Don't look further than arity args, + -- but if there are arity or fewer, see if there's + -- a newtype in the corner where - do_nothing = returnUs [ (fn_id, rhs) ] + (_, tau) = splitForAllTys ty + (arg_tys, res_ty) = splitFunTys tau + +-- If the original function has one-shot arguments, it is important to +-- make the wrapper and worker have corresponding one-shot arguments too. +-- Otherwise we spuriously float stuff out of case-expression join points, +-- which is very annoying. +get_one_shots (Lam b e) + | isId b = isOneShotLambda b : get_one_shots e + | otherwise = get_one_shots e +get_one_shots (Note _ e) = get_one_shots e +get_one_shots other = noOneShotInfo +\end{code} + + + +%************************************************************************ +%* * +\subsection{The worker wrapper core} +%* * +%************************************************************************ + +@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). + +\begin{code} +mkWrapper :: Type -- Wrapper type + -> Int -- Arity + -> [Demand] -- Wrapper strictness info + -> Bool -- Function returns bottom + -> CprInfo -- Wrapper cpr info + -> UniqSM (Id -> CoreExpr) -- Wrapper body, missing worker Id + +mkWrapper fun_ty arity demands res_bot cpr_info + = mkWwBodies fun_ty arity demands res_bot noOneShotInfo cpr_info `thenUs` \ (_, wrap_fn, _) -> + returnUs wrap_fn + +noOneShotInfo = repeat False \end{code} + +