X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Fstranal%2FWorkWrap.lhs;h=d587894ac3c64acb4a8c91d8ef1fd739e73e691f;hb=3a223cd2811d46295048b3a2dab11403ca291b20;hp=bda7de10b176a8933742fcb0c1a44bbc4c806314;hpb=6c381e873e222417d9a67aeec77b9555eca7b7a8;p=ghc-hetmet.git diff --git a/ghc/compiler/stranal/WorkWrap.lhs b/ghc/compiler/stranal/WorkWrap.lhs index bda7de1..d587894 100644 --- a/ghc/compiler/stranal/WorkWrap.lhs +++ b/ghc/compiler/stranal/WorkWrap.lhs @@ -1,54 +1,94 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1993-1995 +% (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 -IMPORT_Trace -import Outputable -import Pretty +#include "HsVersions.h" -import Id ( idType, addIdStrictness, getIdStrictness, - getIdUnfolding, mkWorkerId, - replaceIdInfo, getIdInfo, idWantsToBeINLINEd +import CoreSyn +import CoreUnfold ( certainlyWillInline ) +import CoreLint ( showPass, endPass ) +import CoreUtils ( exprType, exprIsValue ) +import Id ( Id, idType, isOneShotLambda, + setIdNewStrictness, mkWorkerId, + setIdWorkerInfo, setInlinePragma, + idInfo ) +import MkId ( lazyIdKey, lazyIdUnfolding ) +import Type ( Type ) +import IdInfo ( WorkerInfo(..), arityInfo, + newDemandInfo, newStrictnessInfo, unfoldingInfo, inlinePragInfo + ) +import NewDemand ( Demand(..), StrictSig(..), DmdType(..), DmdResult(..), + Demands(..), mkTopDmdType, isBotRes, returnsCPR, topSig, isAbsent ) -import IdInfo -- bits and pieces -import Maybes ( maybeToBool, Maybe(..) ) -import SaLib -import SrcLoc ( mkUnknownSrcLoc, SrcLoc ) -import Util +import UniqSupply ( UniqSupply, initUs_, returnUs, thenUs, mapUs, getUniqueUs, UniqSM ) +import Unique ( hasKey ) +import BasicTypes ( RecFlag(..), isNonRec, Activation(..) ) +import VarEnv ( isEmptyVarEnv ) +import Maybes ( orElse ) +import CmdLineOpts import WwLib +import Util ( lengthIs, notNull ) +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] -> WwM [CoreBinding] -workersAndWrappers top_binds - = mapWw (wwBind True{-top-level-}) top_binds `thenWw` \ top_binds2 -> - let - top_binds3 = map make_top_binding top_binds2 - in - returnWw (concat top_binds3) - where - make_top_binding :: WwBinding -> [CoreBinding] +wwTopBinds :: DynFlags + -> UniqSupply + -> [CoreBind] + -> IO [CoreBind] + +wwTopBinds dflags us binds + = do { + showPass dflags "Worker Wrapper binds"; - make_top_binding (WwLet binds) = 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" + Opt_D_dump_worker_wrapper binds' + } +\end{code} + + +\begin{code} +workersAndWrappers :: UniqSupply -> [CoreBind] -> [CoreBind] + +workersAndWrappers us top_binds + = initUs_ us $ + mapUs wwBind top_binds `thenUs` \ top_binds' -> + returnUs (concat top_binds') \end{code} %************************************************************************ @@ -61,100 +101,71 @@ workersAndWrappers top_binds turn. Non-recursive case first, then recursive... \begin{code} -wwBind :: Bool -- True <=> top-level binding - -> CoreBinding - -> WwM 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 `thenWw` \ new_rhs -> - tryWW binder new_rhs `thenWw` \ new_pairs -> - returnWw (WwLet [NonRec b e | (b,e) <- new_pairs]) +wwBind (NonRec binder rhs) + = wwExpr rhs `thenUs` \ new_rhs -> + tryWW NonRecursive 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) - = mapWw do_one pairs `thenWw` \ new_pairs -> - returnWw (WwLet [Rec (concat new_pairs)]) +wwBind (Rec pairs) + = mapUs do_one pairs `thenUs` \ new_pairs -> + returnUs [Rec (concat new_pairs)] where - do_one (binder, rhs) = wwExpr rhs `thenWw` \ new_rhs -> - tryWW binder new_rhs + do_one (binder, rhs) = wwExpr rhs `thenUs` \ new_rhs -> + tryWW 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 -> WwM CoreExpr - -wwExpr e@(Var _) = returnWw e -wwExpr e@(Lit _) = returnWw e -wwExpr e@(Con _ _ _) = returnWw e -wwExpr e@(Prim _ _ _) = returnWw e +wwExpr :: CoreExpr -> UniqSM CoreExpr -wwExpr (Lam binders expr) - = wwExpr expr `thenWw` \ new_expr -> - returnWw (Lam binders new_expr) +wwExpr e@(Type _) = returnUs e +wwExpr e@(Lit _) = returnUs e +wwExpr e@(Note InlineMe expr) = returnUs e + -- Don't w/w inside InlineMe's -wwExpr (CoTyLam ty expr) - = wwExpr expr `thenWw` \ new_expr -> - returnWw (CoTyLam ty new_expr) +wwExpr e@(Var v) + | v `hasKey` lazyIdKey = returnUs lazyIdUnfolding + | otherwise = returnUs e + -- Inline 'lazy' after strictness analysis + -- (but not inside InlineMe's) -wwExpr (App e1 e2) - = wwExpr e1 `thenWw` \ new_e1 -> - returnWw (App new_e1 e2) +wwExpr (Lam binder expr) + = wwExpr expr `thenUs` \ new_expr -> + returnUs (Lam binder new_expr) -wwExpr (CoTyApp expr ty) - = wwExpr expr `thenWw` \ new_expr -> - returnWw (CoTyApp new_expr ty) +wwExpr (App f a) + = wwExpr f `thenUs` \ new_f -> + wwExpr a `thenUs` \ new_a -> + returnUs (App new_f new_a) -wwExpr (SCC cc expr) - = wwExpr expr `thenWw` \ new_expr -> - returnWw (SCC cc new_expr) +wwExpr (Note note expr) + = wwExpr expr `thenUs` \ new_expr -> + returnUs (Note note new_expr) wwExpr (Let bind expr) - = wwBind False{-not top-level-} bind `thenWw` \ intermediate_bind -> - wwExpr expr `thenWw` \ new_expr -> - returnWw (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 - -wwExpr (Case expr alts) - = wwExpr expr `thenWw` \ new_expr -> - ww_alts alts `thenWw` \ new_alts -> - returnWw (Case new_expr new_alts) + = wwBind bind `thenUs` \ intermediate_bind -> + wwExpr expr `thenUs` \ new_expr -> + returnUs (mkLets intermediate_bind new_expr) + +wwExpr (Case expr binder alts) + = wwExpr expr `thenUs` \ new_expr -> + mapUs ww_alt alts `thenUs` \ new_alts -> + returnUs (Case new_expr binder new_alts) where - ww_alts (AlgAlts alts deflt) - = mapWw ww_alg_alt alts `thenWw` \ new_alts -> - ww_deflt deflt `thenWw` \ new_deflt -> - returnWw (AlgAlts new_alts new_deflt) - - ww_alts (PrimAlts alts deflt) - = mapWw ww_prim_alt alts `thenWw` \ new_alts -> - ww_deflt deflt `thenWw` \ new_deflt -> - returnWw (PrimAlts new_alts new_deflt) - - ww_alg_alt (con, binders, rhs) - = wwExpr rhs `thenWw` \ new_rhs -> - returnWw (con, binders, new_rhs) - - ww_prim_alt (lit, rhs) - = wwExpr rhs `thenWw` \ new_rhs -> - returnWw (lit, new_rhs) - - ww_deflt NoDefault - = returnWw NoDefault - - ww_deflt (BindDefault binder rhs) - = wwExpr rhs `thenWw` \ new_rhs -> - returnWw (BindDefault binder new_rhs) + ww_alt (con, binders, rhs) + = wwExpr rhs `thenUs` \ new_rhs -> + returnUs (con, binders, new_rhs) \end{code} %************************************************************************ @@ -176,78 +187,218 @@ 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 :: RecFlag + -> Id -- The fn binder + -> CoreExpr -- The bound rhs; its innards -- are already ww'd - -> WwM [(Id, CoreExpr)] -- either *one* or *two* pairs; + -> 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 +tryWW is_rec fn_id rhs + | isNonRec is_rec && certainlyWillInline unfolding + -- 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. + -- + -- It's very important to refrain from w/w-ing an INLINE function + -- If we do so by mistake we transform + -- f = __inline (\x -> E) + -- into + -- f = __inline (\x -> case x of (a,b) -> fw E) + -- fw = \ab -> (__inline (\x -> E)) (a,b) + -- and the original __inline now vanishes, so E is no longer + -- inside its __inline wrapper. Death! Disaster! + = returnUs [ (new_fn_id, rhs) ] + + | is_thunk && worthSplittingThunk maybe_fn_dmd res_info + = ASSERT2( isNonRec is_rec, ppr new_fn_id ) -- The thunk must be non-recursive + splitThunk new_fn_id rhs + + | is_fun && worthSplittingFun wrap_dmds res_info + = splitFun new_fn_id fn_info wrap_dmds res_info inline_prag rhs | 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) = digForLambdas rhs - body_ty = coreExprType body - in - uniqSMtoWwM (mkWwBodies body_ty tyvars args args_info) `thenWw` \ 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! - getUniqueWw `thenWw` \ 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 - returnWw [ (worker_id, worker_rhs), -- worker comes first - (wrapper_id, wrapper_rhs) ] -- because wrapper mentions it + = returnUs [ (new_fn_id, rhs) ] + where - do_nothing = returnWw [ (fn_id, rhs) ] + fn_info = idInfo fn_id + maybe_fn_dmd = newDemandInfo fn_info + unfolding = unfoldingInfo fn_info + inline_prag = inlinePragInfo fn_info + maybe_sig = newStrictnessInfo fn_info + + -- In practice it always will have a strictness + -- signature, even if it's a uninformative one + strict_sig = newStrictnessInfo fn_info `orElse` topSig + StrictSig (DmdType env wrap_dmds res_info) = strict_sig + + -- new_fn_id has the DmdEnv zapped. + -- (a) it is never used again + -- (b) it wastes space + -- (c) it becomes incorrect as things are cloned, because + -- we don't push the substitution into it + new_fn_id | isEmptyVarEnv env = fn_id + | otherwise = fn_id `setIdNewStrictness` + StrictSig (mkTopDmdType wrap_dmds res_info) + + is_fun = notNull wrap_dmds + is_thunk = not is_fun && not (exprIsValue rhs) + +--------------------- +splitFun fn_id fn_info wrap_dmds res_info inline_prag rhs + = WARN( not (wrap_dmds `lengthIs` arity), ppr fn_id <+> (ppr arity $$ ppr wrap_dmds $$ ppr res_info) ) + -- The arity should match the signature + mkWwBodies fun_ty wrap_dmds res_info one_shots `thenUs` \ (work_demands, wrap_fn, work_fn) -> + getUniqueUs `thenUs` \ work_uniq -> + let + work_rhs = work_fn rhs + work_id = mkWorkerId work_uniq fn_id (exprType work_rhs) + `setInlinePragma` inline_prag + `setIdNewStrictness` StrictSig (mkTopDmdType work_demands work_res_info) + -- Even though we may not be at top level, + -- it's ok to give it an empty DmdEnv + + wrap_rhs = wrap_fn work_id + wrap_id = fn_id `setIdWorkerInfo` HasWorker work_id arity + `setInlinePragma` AlwaysActive -- Zap any inline pragma; + -- Put it on the worker instead + 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 = arityInfo fn_info -- The arity is set by the simplifier using exprEtaExpandArity + -- So it may be more than the number of top-level-visible lambdas + + work_res_info | isBotRes res_info = BotRes -- Cpr stuff done by wrapper + | otherwise = TopRes + + one_shots = get_one_shots rhs + +-- 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} + +Thunk splitting +~~~~~~~~~~~~~~~ +Suppose x is used strictly (never mind whether it has the CPR +property). + + let + x* = x-rhs + in body + +splitThunk transforms like this: + + let + x* = case x-rhs of { I# a -> I# a } + in body + +Now simplifier will transform to + + case x-rhs of + I# a -> let x* = I# b + in body + +which is what we want. Now suppose x-rhs is itself a case: + + x-rhs = case e of { T -> I# a; F -> I# b } + +The join point will abstract over a, rather than over (which is +what would have happened before) which is fine. + +Notice that x certainly has the CPR property now! + +In fact, splitThunk uses the function argument w/w splitting +function, so that if x's demand is deeper (say U(U(L,L),L)) +then the splitting will go deeper too. + +\begin{code} +-- splitThunk converts the *non-recursive* binding +-- x = e +-- into +-- x = let x = e +-- in case x of +-- I# y -> let x = I# y in x } +-- See comments above. Is it not beautifully short? + +splitThunk fn_id rhs + = mkWWstr [fn_id] `thenUs` \ (_, wrap_fn, work_fn) -> + returnUs [ (fn_id, Let (NonRec fn_id rhs) (wrap_fn (work_fn (Var fn_id)))) ] +\end{code} + + +%************************************************************************ +%* * +\subsection{Functions over Demands} +%* * +%************************************************************************ + +\begin{code} +worthSplittingFun :: [Demand] -> DmdResult -> Bool + -- True <=> the wrapper would not be an identity function +worthSplittingFun ds res + = any worth_it ds || returnsCPR res + -- worthSplitting returns False for an empty list of demands, + -- and hence do_strict_ww is False if arity is zero and there is no CPR + + -- 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. + -- [We don't do reboxing now, but in general it's better to pass + -- an unboxed thing to f, and have it reboxed in the error cases....] + where + worth_it Abs = True -- Absent arg + worth_it (Eval (Prod ds)) = True -- Product arg to evaluate + worth_it other = False + +worthSplittingThunk :: Maybe Demand -- Demand on the thunk + -> DmdResult -- CPR info for the thunk + -> Bool +worthSplittingThunk maybe_dmd res + = worth_it maybe_dmd || returnsCPR res + where + -- Split if the thing is unpacked + worth_it (Just (Eval (Prod ds))) = not (all isAbsent ds) + worth_it other = False +\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 + -> StrictSig -- Wrapper strictness info + -> UniqSM (Id -> CoreExpr) -- Wrapper body, missing worker Id + +mkWrapper fun_ty (StrictSig (DmdType _ demands res_info)) + = mkWwBodies fun_ty demands res_info noOneShotInfo `thenUs` \ (_, wrap_fn, _) -> + returnUs wrap_fn + +noOneShotInfo = repeat False \end{code}