X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FsimplCore%2FOccurAnal.lhs;h=021ee87fdb2dc62294163e4068eb3d7eb2220e10;hb=f2054812b868d752c75dd0b148cc884b00f5e5d6;hp=826f6e1865bd2940768d1f0a9bf412d698721f62;hpb=26aba3b961ef34404137cac0ad9b767e2fda3224;p=ghc-hetmet.git diff --git a/ghc/compiler/simplCore/OccurAnal.lhs b/ghc/compiler/simplCore/OccurAnal.lhs index 826f6e1..021ee87 100644 --- a/ghc/compiler/simplCore/OccurAnal.lhs +++ b/ghc/compiler/simplCore/OccurAnal.lhs @@ -17,30 +17,28 @@ module OccurAnal ( #include "HsVersions.h" -import BinderInfo import CoreSyn import CoreFVs ( idRuleVars ) import CoreUtils ( exprIsTrivial ) import Id ( isDataConId, isOneShotLambda, setOneShotLambda, idOccInfo, setIdOccInfo, - isExportedId, modifyIdInfo, idInfo, - idSpecialisation, + isExportedId, modifyIdInfo, idInfo, idArity, + idSpecialisation, isLocalId, idType, idUnique, Id ) -import IdInfo ( OccInfo(..), shortableIdInfo, copyIdInfo ) +import IdInfo ( shortableIdInfo, copyIdInfo ) +import BasicTypes ( OccInfo(..), isOneOcc ) import VarSet import VarEnv -import Name ( isLocallyDefined ) import Type ( splitFunTy_maybe, splitForAllTys ) -import Maybes ( maybeToBool ) +import Maybes ( maybeToBool, orElse ) import Digraph ( stronglyConnCompR, SCC(..) ) import PrelNames ( buildIdKey, foldrIdKey, runSTRepIdKey, augmentIdKey ) -import Unique ( u2i ) +import Unique ( Unique ) import UniqFM ( keysUFM ) import Util ( zipWithEqual, mapAndUnzip ) -import FastTypes import Outputable \end{code} @@ -54,29 +52,19 @@ import Outputable Here's the externally-callable interface: \begin{code} -occurAnalyseExpr :: (Id -> Bool) -- Tells if a variable is interesting - -> CoreExpr - -> (IdEnv BinderInfo, -- Occ info for interesting free vars - CoreExpr) - -occurAnalyseExpr interesting expr - = occAnal initial_env expr - where - initial_env = OccEnv interesting emptyVarSet [] - occurAnalyseGlobalExpr :: CoreExpr -> CoreExpr occurAnalyseGlobalExpr expr = -- Top level expr, so no interesting free vars, and -- discard occurence info returned - snd (occurAnalyseExpr (\_ -> False) expr) + snd (occAnal (initOccEnv emptyVarSet) expr) occurAnalyseRule :: CoreRule -> CoreRule -occurAnalyseRule rule@(BuiltinRule _) = rule -occurAnalyseRule (Rule str tpl_vars tpl_args rhs) +occurAnalyseRule rule@(BuiltinRule _ _) = rule +occurAnalyseRule (Rule str act tpl_vars tpl_args rhs) -- Add occ info to tpl_vars, rhs - = Rule str tpl_vars' tpl_args rhs' + = Rule str act tpl_vars' tpl_args rhs' where - (rhs_uds, rhs') = occurAnalyseExpr isLocallyDefined rhs + (rhs_uds, rhs') = occAnal (initOccEnv (mkVarSet tpl_vars)) rhs (_, tpl_vars') = tagBinders rhs_uds tpl_vars \end{code} @@ -139,7 +127,7 @@ occurAnalyseBinds :: [CoreBind] -> [CoreBind] occurAnalyseBinds binds = binds' where - (_, _, binds') = go initialTopEnv binds + (_, _, binds') = go (initOccEnv emptyVarSet) binds go :: OccEnv -> [CoreBind] -> (UsageDetails, -- Occurrence info @@ -175,10 +163,6 @@ occurAnalyseBinds binds other -> -- Ho ho! The normal case (final_usage, ind_env, new_binds ++ binds') -initialTopEnv = OccEnv isLocallyDefined -- Anything local is interesting - emptyVarSet - [] - -- Deal with any indirections zapBind ind_env (NonRec bndr rhs) @@ -202,7 +186,7 @@ shortMeOut ind_env exported_id local_id -- how often I don't get shorting out becuase of IdInfo stuff = if isExportedId exported_id && -- Only if this is exported - isLocallyDefined local_id && -- Only if this one is defined in this + isLocalId local_id && -- Only if this one is defined in this -- module, so that we *can* change its -- binding to be the exported thing! @@ -211,10 +195,18 @@ shortMeOut ind_env exported_id local_id not (local_id `elemVarEnv` ind_env) -- Only if not already substituted for then + True + +{- No longer needed if shortableIdInfo (idInfo exported_id) -- Only if its IdInfo is 'shortable' - -- (see the defn of IdInfo.shortableIdInfo + -- (see the defn of IdInfo.shortableIdInfo) then True - else pprTrace "shortMeOut:" (ppr exported_id) False + else +#ifdef DEBUG + pprTrace "shortMeOut:" (ppr exported_id) +#endif + False +-} else False \end{code} @@ -232,7 +224,7 @@ Bindings \begin{code} type IdWithOccInfo = Id -- An Id with fresh PragmaInfo attached -type Node details = (details, Int, [Int]) -- The Ints are gotten from the Unique, +type Node details = (details, Unique, [Unique]) -- The Ints are gotten from the Unique, -- which is gotten from the Id. type Details1 = (Id, UsageDetails, CoreExpr) type Details2 = (IdWithOccInfo, CoreExpr) @@ -312,7 +304,7 @@ occAnalBind env (Rec pairs) body_usage ---- stuff for dependency analysis of binds ------------------------------- edges :: [Node Details1] edges = _scc_ "occAnalBind.assoc" - [ (details, iBox (u2i (idUnique id)), edges_from rhs_usage) + [ (details, idUnique id, edges_from rhs_usage) | details@(id, rhs_usage, rhs) <- analysed_pairs ] @@ -325,7 +317,7 @@ occAnalBind env (Rec pairs) body_usage -- maybeToBool (lookupVarEnv rhs_usage bndr)] -- which has n**2 cost, and this meant that edges_from alone -- consumed 10% of total runtime! - edges_from :: UsageDetails -> [Int] + edges_from :: UsageDetails -> [Unique] edges_from rhs_usage = _scc_ "occAnalBind.edges_from" keysUFM rhs_usage @@ -481,9 +473,7 @@ reOrderRec env (CyclicSCC (bind : binds)) inlineCandidate :: Id -> CoreExpr -> Bool inlineCandidate id (Note InlineMe _) = True - inlineCandidate id rhs = case idOccInfo id of - OneOcc _ _ -> True - other -> False + inlineCandidate id rhs = isOneOcc (idOccInfo id) -- Real example (the Enum Ordering instance from PrelBase): -- rec f = \ x -> case d of (p,q,r) -> p x @@ -519,7 +509,21 @@ occAnalRhs :: OccEnv occAnalRhs env id rhs = (final_usage, rhs') where - (rhs_usage, rhs') = occAnal (zapCtxt env) rhs + (rhs_usage, rhs') = occAnal (rhsCtxt env) rhs + -- Note that we use an rhsCtxt. This tells the occ anal that it's + -- looking at an RHS, which has an effect in occAnalApp + -- + -- But there's a problem. Consider + -- x1 = a0 : [] + -- x2 = a1 : x1 + -- x3 = a2 : x2 + -- g = f x2 + -- First time round, it looks as if x1 and x2 occur as an arg of a + -- let-bound constructor ==> give them a many-occurrence. + -- But then x3 is inlined (unconditionally as it happens) and + -- next time round, x2 will be, and the next time round x1 will be + -- Result: multiple simplifier iterations. Sigh. + -- Possible solution: use rhsCtxt for things that occur just once... -- [March 98] A new wrinkle is that if the binder has specialisations inside -- it then we count the specialised Ids as "extra rhs's". That way @@ -528,7 +532,7 @@ occAnalRhs env id rhs -- die too unless they are already referenced directly. final_usage = foldVarSet add rhs_usage (idRuleVars id) - add v u = addOneOcc u v noBinderInfo -- Give a non-committal binder info + add v u = addOneOcc u v NoOccInfo -- Give a non-committal binder info -- (i.e manyOcc) because many copies -- of the specialised thing can appear \end{code} @@ -546,7 +550,7 @@ occAnal env (Type t) = (emptyDetails, Type t) occAnal env (Var v) = (var_uds, Var v) where - var_uds | isCandidate env v = unitVarEnv v funOccZero + var_uds | isCandidate env v = unitVarEnv v oneOcc | otherwise = emptyDetails -- At one stage, I gathered the idRuleVars for v here too, @@ -596,7 +600,7 @@ occAnal env (Note note body) \begin{code} occAnal env app@(App fun arg) - = occAnalApp env (collectArgs app) + = occAnalApp env (collectArgs app) False -- Ignore type variables altogether -- (a) occurrences inside type lambdas only not marked as InsideLam @@ -617,7 +621,7 @@ occAnal env expr@(Lam x body) | isTyVar x -- Then, the simplifier is careful when partially applying lambdas. occAnal env expr@(Lam _ _) - = case occAnal (env_body `addNewCands` binders) body of { (body_usage, body') -> + = case occAnal env_body body of { (body_usage, body') -> let (final_usage, tagged_binders) = tagBinders body_usage binders -- URGH! Sept 99: we don't seem to be able to use binders' here, because @@ -632,12 +636,15 @@ occAnal env expr@(Lam _ _) (really_final_usage, mkLams tagged_binders body') } where - (binders, body) = collectBinders expr - (linear, env_body, _) = oneShotGroup env binders + (binders, body) = collectBinders expr + (linear, env1, _) = oneShotGroup env binders + env2 = env1 `addNewCands` binders -- Add in-scope binders + env_body = vanillaCtxt env2 -- Body is (no longer) an RhsContext occAnal env (Case scrut bndr alts) - = case mapAndUnzip (occAnalAlt alt_env) alts of { (alts_usage_s, alts') -> - case occAnal (zapCtxt env) scrut of { (scrut_usage, scrut') -> + = case mapAndUnzip (occAnalAlt alt_env bndr) alts of { (alts_usage_s, alts') -> + case occAnal (vanillaCtxt env) scrut of { (scrut_usage, scrut') -> + -- No need for rhsCtxt let alts_usage = foldr1 combineAltsUsageDetails alts_usage_s alts_usage' = addCaseBndrUsage alts_usage @@ -670,7 +677,7 @@ occAnalArgs env args = case mapAndUnzip (occAnal arg_env) args of { (arg_uds_s, args') -> (foldr combineUsageDetails emptyDetails arg_uds_s, args')} where - arg_env = zapCtxt env + arg_env = vanillaCtxt env \end{code} Applications are dealt with specially because we want @@ -678,54 +685,75 @@ the "build hack" to work. \begin{code} -- Hack for build, fold, runST -occAnalApp env (Var fun, args) +occAnalApp env (Var fun, args) is_rhs = case args_stuff of { (args_uds, args') -> let - final_uds = fun_uds `combineUsageDetails` args_uds + -- We mark the free vars of the argument of a constructor or PAP + -- as "many", if it is the RHS of a let(rec). + -- This means that nothing gets inlined into a constructor argument + -- position, which is what we want. Typically those constructor + -- arguments are just variables, or trivial expressions. + -- + -- This is the *whole point* of the isRhsEnv predicate + final_args_uds + | isRhsEnv env, + isDataConId fun || valArgCount args < idArity fun + = mapVarEnv markMany args_uds + | otherwise = args_uds in - (final_uds, mkApps (Var fun) args') } + (fun_uds `combineUsageDetails` final_args_uds, mkApps (Var fun) args') } where fun_uniq = idUnique fun - fun_uds | isCandidate env fun = unitVarEnv fun funOccZero + fun_uds | isCandidate env fun = unitVarEnv fun oneOcc | otherwise = emptyDetails args_stuff | fun_uniq == buildIdKey = appSpecial env 2 [True,True] args | fun_uniq == augmentIdKey = appSpecial env 2 [True,True] args | fun_uniq == foldrIdKey = appSpecial env 3 [False,True] args - | fun_uniq == runSTRepIdKey = appSpecial env 2 [True] args - - | isDataConId fun = case occAnalArgs env args of - (arg_uds, args') -> (mapVarEnv markMany arg_uds, args') - -- We mark the free vars of the argument of a constructor as "many" - -- This means that nothing gets inlined into a constructor argument - -- position, which is what we want. Typically those constructor - -- arguments are just variables, or trivial expressions. - - | otherwise = occAnalArgs env args - - -occAnalApp env (fun, args) - = case occAnal (zapCtxt env) fun of { (fun_uds, fun') -> - case occAnalArgs env args of { (args_uds, args') -> + | fun_uniq == runSTRepIdKey = appSpecial env 2 [True] args + -- (foldr k z xs) may call k many times, but it never + -- shares a partial application of k; hence [False,True] + -- This means we can optimise + -- foldr (\x -> let v = ...x... in \y -> ...v...) z xs + -- by floating in the v + + | otherwise = occAnalArgs env args + + +occAnalApp env (fun, args) is_rhs + = case occAnal (addAppCtxt env args) fun of { (fun_uds, fun') -> + -- The addAppCtxt is a bit cunning. One iteration of the simplifier + -- often leaves behind beta redexs like + -- (\x y -> e) a1 a2 + -- Here we would like to mark x,y as one-shot, and treat the whole + -- thing much like a let. We do this by pushing some True items + -- onto the context stack. + + case occAnalArgs env args of { (args_uds, args') -> let final_uds = fun_uds `combineUsageDetails` args_uds in (final_uds, mkApps fun' args') }} -appSpecial :: OccEnv -> Int -> CtxtTy -> [CoreExpr] -> (UsageDetails, [CoreExpr]) +appSpecial :: OccEnv + -> Int -> CtxtTy -- Argument number, and context to use for it + -> [CoreExpr] + -> (UsageDetails, [CoreExpr]) appSpecial env n ctxt args = go n args where + arg_env = vanillaCtxt env + go n [] = (emptyDetails, []) -- Too few args go 1 (arg:args) -- The magic arg - = case occAnal (setCtxt env ctxt) arg of { (arg_uds, arg') -> - case occAnalArgs env args of { (args_uds, args') -> + = case occAnal (setCtxt arg_env ctxt) arg of { (arg_uds, arg') -> + case occAnalArgs env args of { (args_uds, args') -> (combineUsageDetails arg_uds args_uds, arg':args') }} go n (arg:args) - = case occAnal env arg of { (arg_uds, arg') -> + = case occAnal arg_env arg of { (arg_uds, arg') -> case go (n-1) args of { (args_uds, args') -> (combineUsageDetails arg_uds args_uds, arg':args') }} \end{code} @@ -733,31 +761,53 @@ appSpecial env n ctxt args Case alternatives ~~~~~~~~~~~~~~~~~ +If the case binder occurs at all, the other binders effectively do too. +For example + case e of x { (a,b) -> rhs } +is rather like + let x = (a,b) in rhs +If e turns out to be (e1,e2) we indeed get something like + let a = e1; b = e2; x = (a,b) in rhs + \begin{code} -occAnalAlt env (con, bndrs, rhs) +occAnalAlt env case_bndr (con, bndrs, rhs) = case occAnal (env `addNewCands` bndrs) rhs of { (rhs_usage, rhs') -> let (final_usage, tagged_bndrs) = tagBinders rhs_usage bndrs + final_bndrs | case_bndr `elemVarEnv` final_usage = bndrs + | otherwise = tagged_bndrs + -- Leave the binders untagged if the case + -- binder occurs at all; see note above in - (final_usage, (con, tagged_bndrs, rhs')) } + (final_usage, (con, final_bndrs, rhs')) } \end{code} %************************************************************************ %* * -\subsection[OccurAnal-types]{Data types} +\subsection[OccurAnal-types]{OccEnv} %* * %************************************************************************ \begin{code} --- We gather inforamtion for variables that are either --- (a) in scope or --- (b) interesting - -data OccEnv = - OccEnv (Id -> Bool) -- Tells whether an Id occurrence is interesting, - IdSet -- In-scope Ids - CtxtTy -- Tells about linearity +data OccEnv + = OccEnv IdSet -- In-scope Ids; we gather info about these only + OccEncl -- Enclosing context information + CtxtTy -- Tells about linearity + +-- OccEncl is used to control whether to inline into constructor arguments +-- For example: +-- x = (p,q) -- Don't inline p or q +-- y = /\a -> (p a, q a) -- Still don't inline p or q +-- z = f (p,q) -- Do inline p,q; it may make a rule fire +-- So OccEncl tells enought about the context to know what to do when +-- we encounter a contructor application or PAP. + +data OccEncl + = OccRhs -- RHS of let(rec), albeit perhaps inside a type lambda + -- Don't inline into constructor args here + | OccVanilla -- Argument of function, body of lambda, scruintee of case etc. + -- Do inline into constructor args here type CtxtTy = [Bool] -- [] No info @@ -769,19 +819,25 @@ type CtxtTy = [Bool] -- be applied many times; but when it is, -- the CtxtTy inside applies +initOccEnv :: VarSet -> OccEnv +initOccEnv vars = OccEnv vars OccRhs [] + +isRhsEnv (OccEnv _ OccRhs _) = True +isRhsEnv (OccEnv _ OccVanilla _) = False + isCandidate :: OccEnv -> Id -> Bool -isCandidate (OccEnv ifun cands _) id = id `elemVarSet` cands || ifun id +isCandidate (OccEnv cands encl _) id = id `elemVarSet` cands addNewCands :: OccEnv -> [Id] -> OccEnv -addNewCands (OccEnv ifun cands ctxt) ids - = OccEnv ifun (cands `unionVarSet` mkVarSet ids) ctxt +addNewCands (OccEnv cands encl ctxt) ids + = OccEnv (cands `unionVarSet` mkVarSet ids) encl ctxt addNewCand :: OccEnv -> Id -> OccEnv -addNewCand (OccEnv ifun cands ctxt) id - = OccEnv ifun (extendVarSet cands id) ctxt +addNewCand (OccEnv cands encl ctxt) id + = OccEnv (extendVarSet cands id) encl ctxt setCtxt :: OccEnv -> CtxtTy -> OccEnv -setCtxt (OccEnv ifun cands _) ctxt = OccEnv ifun cands ctxt +setCtxt (OccEnv cands encl _) ctxt = OccEnv cands encl ctxt oneShotGroup :: OccEnv -> [CoreBndr] -> (Bool, OccEnv, [CoreBndr]) -- True <=> this is a one-shot linear lambda group @@ -792,9 +848,9 @@ oneShotGroup :: OccEnv -> [CoreBndr] -> (Bool, OccEnv, [CoreBndr]) -- linearity context knows that c,n are one-shot, and it records that fact in -- the binder. This is useful to guide subsequent float-in/float-out tranformations -oneShotGroup (OccEnv ifun cands ctxt) bndrs +oneShotGroup (OccEnv cands encl ctxt) bndrs = case go ctxt bndrs [] of - (new_ctxt, new_bndrs) -> (all is_one_shot new_bndrs, OccEnv ifun cands new_ctxt, new_bndrs) + (new_ctxt, new_bndrs) -> (all is_one_shot new_bndrs, OccEnv cands encl new_ctxt, new_bndrs) where is_one_shot b = isId b && isOneShotLambda b @@ -809,29 +865,38 @@ oneShotGroup (OccEnv ifun cands ctxt) bndrs go ctxt (bndr:bndrs) rev_bndrs = go ctxt bndrs (bndr:rev_bndrs) -zapCtxt env@(OccEnv ifun cands []) = env -zapCtxt (OccEnv ifun cands _ ) = OccEnv ifun cands [] +vanillaCtxt (OccEnv cands _ _) = OccEnv cands OccVanilla [] +rhsCtxt (OccEnv cands _ _) = OccEnv cands OccRhs [] + +addAppCtxt (OccEnv cands encl ctxt) args + = OccEnv cands encl (replicate (valArgCount args) True ++ ctxt) +\end{code} + +%************************************************************************ +%* * +\subsection[OccurAnal-types]{OccEnv} +%* * +%************************************************************************ -type UsageDetails = IdEnv BinderInfo -- A finite map from ids to their usage +\begin{code} +type UsageDetails = IdEnv OccInfo -- A finite map from ids to their usage combineUsageDetails, combineAltsUsageDetails :: UsageDetails -> UsageDetails -> UsageDetails combineUsageDetails usage1 usage2 - = plusVarEnv_C addBinderInfo usage1 usage2 + = plusVarEnv_C addOccInfo usage1 usage2 combineAltsUsageDetails usage1 usage2 - = plusVarEnv_C orBinderInfo usage1 usage2 + = plusVarEnv_C orOccInfo usage1 usage2 -addOneOcc :: UsageDetails -> Id -> BinderInfo -> UsageDetails +addOneOcc :: UsageDetails -> Id -> OccInfo -> UsageDetails addOneOcc usage id info - = plusVarEnv_C addBinderInfo usage (unitVarEnv id info) + = plusVarEnv_C addOccInfo usage (unitVarEnv id info) -- ToDo: make this more efficient emptyDetails = (emptyVarEnv :: UsageDetails) -unitDetails id info = (unitVarEnv id info :: UsageDetails) - usedIn :: Id -> UsageDetails -> Bool v `usedIn` details = isExportedId v || v `elemVarEnv` details @@ -859,23 +924,57 @@ tagBinder usage binder in usage' `seq` (usage', binder') - setBinderOcc :: UsageDetails -> CoreBndr -> CoreBndr setBinderOcc usage bndr | isTyVar bndr = bndr - | isExportedId bndr - = -- Don't use local usage info for visible-elsewhere things - -- BUT *do* erase any IAmALoopBreaker annotation, because we're - -- about to re-generate it and it shouldn't be "sticky" - case idOccInfo bndr of - NoOccInfo -> bndr - other -> setIdOccInfo bndr NoOccInfo + | isExportedId bndr = case idOccInfo bndr of + NoOccInfo -> bndr + other -> setIdOccInfo bndr NoOccInfo + -- Don't use local usage info for visible-elsewhere things + -- BUT *do* erase any IAmALoopBreaker annotation, because we're + -- about to re-generate it and it shouldn't be "sticky" - | otherwise = setIdOccInfo bndr occ_info + | otherwise = setIdOccInfo bndr occ_info where - occ_info = case lookupVarEnv usage bndr of - Nothing -> IAmDead - Just info -> binderInfoToOccInfo info + occ_info = lookupVarEnv usage bndr `orElse` IAmDead +\end{code} + + +%************************************************************************ +%* * +\subsection{Operations over OccInfo} +%* * +%************************************************************************ + +\begin{code} +oneOcc :: OccInfo +oneOcc = OneOcc False True + +markMany, markInsideLam, markInsideSCC :: OccInfo -> OccInfo + +markMany IAmDead = IAmDead +markMany other = NoOccInfo + +markInsideSCC occ = markMany occ + +markInsideLam (OneOcc _ one_br) = OneOcc True one_br +markInsideLam occ = occ + +addOccInfo, orOccInfo :: OccInfo -> OccInfo -> OccInfo + +addOccInfo IAmDead info2 = info2 +addOccInfo info1 IAmDead = info1 +addOccInfo info1 info2 = NoOccInfo + +-- (orOccInfo orig new) is used +-- when combining occurrence info from branches of a case + +orOccInfo IAmDead info2 = info2 +orOccInfo info1 IAmDead = info1 +orOccInfo (OneOcc in_lam1 one_branch1) + (OneOcc in_lam2 one_branch2) + = OneOcc (in_lam1 || in_lam2) + False -- False, because it occurs in both branches -funOccZero = funOccurrence 0 +orOccInfo info1 info2 = NoOccInfo \end{code}