X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FsimplCore%2FSetLevels.lhs;h=d0914c948bfd68c97e57096f04e43729dd5e793c;hp=270ce170950160db4b9aae9944277cf5e49c66ce;hb=b84ba676034763b3082bbd9405794a4fde499d14;hpb=e79c9ce01d0ce4412bd4bcd99c8c728a6a2ec569 diff --git a/compiler/simplCore/SetLevels.lhs b/compiler/simplCore/SetLevels.lhs index 270ce17..d0914c9 100644 --- a/compiler/simplCore/SetLevels.lhs +++ b/compiler/simplCore/SetLevels.lhs @@ -48,7 +48,7 @@ module SetLevels ( Level(..), tOP_LEVEL, LevelledBind, LevelledExpr, - incMinorLvl, ltMajLvl, ltLvl, isTopLvl, isInlineCtxt + incMinorLvl, ltMajLvl, ltLvl, isTopLvl ) where #include "HsVersions.h" @@ -56,22 +56,25 @@ module SetLevels ( import CoreSyn import DynFlags ( FloatOutSwitches(..) ) -import CoreUtils ( exprType, exprIsTrivial, mkPiTypes ) +import CoreUtils ( exprType, mkPiTypes ) +import CoreArity ( exprBotStrictness_maybe ) import CoreFVs -- all of it -import CoreSubst ( Subst, emptySubst, extendInScope, extendIdSubst, - cloneIdBndr, cloneRecIdBndrs ) -import Id ( Id, idType, mkSysLocal, isOneShotLambda, +import CoreSubst ( Subst, emptySubst, extendInScope, extendInScopeList, + extendIdSubst, cloneIdBndr, cloneRecIdBndrs ) +import Id ( idType, mkLocalIdWithInfo, mkSysLocal, isOneShotLambda, zapDemandIdInfo, transferPolyIdInfo, - idSpecialisation, idWorkerInfo, setIdInfo + idSpecialisation, idUnfolding, setIdInfo, + setIdStrictness, setIdArity ) import IdInfo import Var import VarSet import VarEnv -import Name ( getOccName ) +import Demand ( StrictSig, increaseStrictSigArity ) +import Name ( getOccName, mkSystemVarName ) import OccName ( occNameString ) import Type ( isUnLiftedType, Type ) -import BasicTypes ( TopLevelFlag(..) ) +import BasicTypes ( TopLevelFlag(..), Arity ) import UniqSupply import Util ( sortLe, isSingleton, count ) import Outputable @@ -85,9 +88,7 @@ import FastString %************************************************************************ \begin{code} -data Level = InlineCtxt -- A level that's used only for - -- the context parameter ctxt_lvl - | Level Int -- Level number of enclosing lambdas +data Level = Level Int -- Level number of enclosing lambdas Int -- Number of big-lambda and/or case expressions between -- here and the nearest enclosing lambda \end{code} @@ -150,55 +151,37 @@ the worker at all. type LevelledExpr = TaggedExpr Level type LevelledBind = TaggedBind Level -tOP_LEVEL, iNLINE_CTXT :: Level +tOP_LEVEL :: Level tOP_LEVEL = Level 0 0 -iNLINE_CTXT = InlineCtxt incMajorLvl :: Level -> Level --- For InlineCtxt we ignore any inc's; we don't want --- to do any floating at all; see notes above -incMajorLvl InlineCtxt = InlineCtxt incMajorLvl (Level major _) = Level (major + 1) 0 incMinorLvl :: Level -> Level -incMinorLvl InlineCtxt = InlineCtxt incMinorLvl (Level major minor) = Level major (minor+1) maxLvl :: Level -> Level -> Level -maxLvl InlineCtxt l2 = l2 -maxLvl l1 InlineCtxt = l1 maxLvl l1@(Level maj1 min1) l2@(Level maj2 min2) | (maj1 > maj2) || (maj1 == maj2 && min1 > min2) = l1 | otherwise = l2 ltLvl :: Level -> Level -> Bool -ltLvl _ InlineCtxt = False -ltLvl InlineCtxt (Level _ _) = True ltLvl (Level maj1 min1) (Level maj2 min2) = (maj1 < maj2) || (maj1 == maj2 && min1 < min2) ltMajLvl :: Level -> Level -> Bool -- Tells if one level belongs to a difft *lambda* level to another -ltMajLvl _ InlineCtxt = False -ltMajLvl InlineCtxt (Level maj2 _) = 0 < maj2 ltMajLvl (Level maj1 _) (Level maj2 _) = maj1 < maj2 isTopLvl :: Level -> Bool isTopLvl (Level 0 0) = True isTopLvl _ = False -isInlineCtxt :: Level -> Bool -isInlineCtxt InlineCtxt = True -isInlineCtxt _ = False - instance Outputable Level where - ppr InlineCtxt = text "" ppr (Level maj min) = hcat [ char '<', int maj, char ',', int min, char '>' ] instance Eq Level where - InlineCtxt == InlineCtxt = True (Level maj1 min1) == (Level maj2 min2) = maj1 == maj2 && min1 == min2 - _ == _ = False \end{code} @@ -215,21 +198,17 @@ setLevels :: FloatOutSwitches -> [LevelledBind] setLevels float_lams binds us - = initLvl us (do_them binds) + = initLvl us (do_them init_env binds) where - -- "do_them"'s main business is to thread the monad along - -- It gives each top binding the same empty envt, because - -- things unbound in the envt have level number zero implicitly - do_them :: [CoreBind] -> LvlM [LevelledBind] - - do_them [] = return [] - do_them (b:bs) = do - (lvld_bind, _) <- lvlTopBind init_env b - lvld_binds <- do_them bs - return (lvld_bind : lvld_binds) - init_env = initialEnv float_lams + do_them :: LevelEnv -> [CoreBind] -> LvlM [LevelledBind] + do_them _ [] = return [] + do_them env (b:bs) + = do { (lvld_bind, env') <- lvlTopBind env b + ; lvld_binds <- do_them env' bs + ; return (lvld_bind : lvld_binds) } + lvlTopBind :: LevelEnv -> Bind Id -> LvlM (LevelledBind, LevelEnv) lvlTopBind env (NonRec binder rhs) = lvlBind TopLevel tOP_LEVEL env (AnnNonRec binder (freeVars rhs)) @@ -273,20 +252,9 @@ lvlExpr _ env (_, AnnVar v) = return (lookupVar env v) lvlExpr _ _ (_, AnnLit lit) = return (Lit lit) lvlExpr ctxt_lvl env (_, AnnApp fun arg) = do - fun' <- lvl_fun fun + fun' <- lvlExpr ctxt_lvl env fun -- We don't do MFE on partial applications arg' <- lvlMFE False ctxt_lvl env arg return (App fun' arg') - where --- gaw 2004 - lvl_fun (_, AnnCase _ _ _ _) = lvlMFE True ctxt_lvl env fun - lvl_fun _ = lvlExpr ctxt_lvl env fun - -- We don't do MFE on partial applications generally, - -- but we do if the function is big and hairy, like a case - -lvlExpr _ env (_, AnnNote InlineMe expr) = do --- Don't float anything out of an InlineMe; hence the iNLINE_CTXT - expr' <- lvlExpr iNLINE_CTXT env expr - return (Note InlineMe expr') lvlExpr ctxt_lvl env (_, AnnNote note expr) = do expr' <- lvlExpr ctxt_lvl env expr @@ -359,13 +327,48 @@ lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr ty alts) = do the expression, so that it can itself be floated. Note [Unlifted MFEs] -~~~~~~~~~~~~~~~~~~~~~ +~~~~~~~~~~~~~~~~~~~~ We don't float unlifted MFEs, which potentially loses big opportunites. For example: \x -> f (h y) where h :: Int -> Int# is expensive. We'd like to float the (h y) outside the \x, but we don't because it's unboxed. Possible solution: box it. +Note [Bottoming floats] +~~~~~~~~~~~~~~~~~~~~~~~ +If we see + f = \x. g (error "urk") +we'd like to float the call to error, to get + lvl = error "urk" + f = \x. g lvl +Furthermore, we want to float a bottoming expression even if it has free +variables: + f = \x. g (let v = h x in error ("urk" ++ v)) +Then we'd like to abstact over 'x' can float the whole arg of g: + lvl = \x. let v = h x in error ("urk" ++ v) + f = \x. g (lvl x) +See Maessen's paper 1999 "Bottom extraction: factoring error handling out +of functional programs" (unpublished I think). + +When we do this, we set the strictness and arity of the new bottoming +Id, so that it's properly exposed as such in the interface file, even if +this is all happening after strictness analysis. + +Note [Bottoming floats: eta expansion] c.f Note [Bottoming floats] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Tiresomely, though, the simplifier has an invariant that the manifest +arity of the RHS should be the same as the arity; but we can't call +etaExpand during SetLevels because it works over a decorated form of +CoreExpr. So we do the eta expansion later, in FloatOut. + +Note [Case MFEs] +~~~~~~~~~~~~~~~~ +We don't float a case expression as an MFE from a strict context. Why not? +Because in doing so we share a tiny bit of computation (the switch) but +in exchange we build a thunk, which is bad. This case reduces allocation +by 7% in spectral/puzzle (a rather strange benchmark) and 1.2% in real/fem. +Doesn't change any other allocation at all. + \begin{code} lvlMFE :: Bool -- True <=> strict context [body of case or let] -> Level -- Level of innermost enclosing lambda/tylam @@ -376,31 +379,39 @@ lvlMFE :: Bool -- True <=> strict context [body of case or let] lvlMFE _ _ _ (_, AnnType ty) = return (Type ty) --- No point in floating out an expression wrapped in a coercion; +-- No point in floating out an expression wrapped in a coercion or note -- If we do we'll transform lvl = e |> co -- to lvl' = e; lvl = lvl' |> co -- and then inline lvl. Better just to float out the payload. +lvlMFE strict_ctxt ctxt_lvl env (_, AnnNote n e) + = do { e' <- lvlMFE strict_ctxt ctxt_lvl env e + ; return (Note n e') } + lvlMFE strict_ctxt ctxt_lvl env (_, AnnCast e co) - = do { expr' <- lvlMFE strict_ctxt ctxt_lvl env e - ; return (Cast expr' co) } + = do { e' <- lvlMFE strict_ctxt ctxt_lvl env e + ; return (Cast e' co) } + +-- Note [Case MFEs] +lvlMFE True ctxt_lvl env e@(_, AnnCase {}) + = lvlExpr ctxt_lvl env e -- Don't share cases lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _) | isUnLiftedType ty -- Can't let-bind it; see Note [Unlifted MFEs] - || isInlineCtxt ctxt_lvl -- Don't float out of an __inline__ context - || exprIsTrivial expr -- Never float if it's trivial + || notWorthFloating ann_expr abs_vars || not good_destination = -- Don't float it out lvlExpr ctxt_lvl env ann_expr | otherwise -- Float it out! = do expr' <- lvlFloatRhs abs_vars dest_lvl env ann_expr - var <- newLvlVar "lvl" abs_vars ty + var <- newLvlVar abs_vars ty mb_bot return (Let (NonRec (TB var dest_lvl) expr') (mkVarApps (Var var) abs_vars)) where expr = deAnnotate ann_expr ty = exprType expr - dest_lvl = destLevel env fvs (isFunction ann_expr) + mb_bot = exprBotStrictness_maybe expr + dest_lvl = destLevel env fvs (isFunction ann_expr) mb_bot abs_vars = abstractVars dest_lvl env fvs -- A decision to float entails let-binding this thing, and we only do @@ -427,6 +438,42 @@ lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _) -- concat = /\ a -> lvl a -- lvl = /\ a -> foldr ..a.. (++) [] -- which is pretty stupid. Hence the strict_ctxt test + +annotateBotStr :: Id -> Maybe (Arity, StrictSig) -> Id +annotateBotStr id Nothing = id +annotateBotStr id (Just (arity,sig)) = id `setIdArity` arity + `setIdStrictness` sig + +notWorthFloating :: CoreExprWithFVs -> [Var] -> Bool +-- Returns True if the expression would be replaced by +-- something bigger than it is now. For example: +-- abs_vars = tvars only: return True if e is trivial, +-- but False for anything bigger +-- abs_vars = [x] (an Id): return True for trivial, or an application (f x) +-- but False for (f x x) +-- +-- One big goal is that floating should be idempotent. Eg if +-- we replace e with (lvl79 x y) and then run FloatOut again, don't want +-- to replace (lvl79 x y) with (lvl83 x y)! + +notWorthFloating e abs_vars + = go e (count isId abs_vars) + where + go (_, AnnVar {}) n = n == 0 + go (_, AnnLit {}) n = n == 0 + go (_, AnnCast e _) n = go e n + go (_, AnnApp e arg) n + | (_, AnnType {}) <- arg = go e n + | n==0 = False + | is_triv arg = go e (n-1) + | otherwise = False + go _ _ = False + + is_triv (_, AnnLit {}) = True -- Treat all literals as trivial + is_triv (_, AnnVar {}) = True -- (ie not worth floating) + is_triv (_, AnnCast e _) = is_triv e + is_triv (_, AnnApp e (_, AnnType {})) = is_triv e + is_triv _ = False \end{code} Note [Escaping a value lambda] @@ -491,7 +538,6 @@ lvlBind :: TopLevelFlag -- Used solely to decide whether to clone lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_)) | isTyVar bndr -- Don't do anything for TyVar binders -- (simplifier gets rid of them pronto) - || isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe = do rhs' <- lvlExpr ctxt_lvl env rhs return (NonRec (TB bndr ctxt_lvl) rhs', env) @@ -504,28 +550,26 @@ lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_)) | otherwise = do -- Yes, type abstraction; create a new binder, extend substitution, etc rhs' <- lvlFloatRhs abs_vars dest_lvl env rhs - (env', [bndr']) <- newPolyBndrs dest_lvl env abs_vars [bndr] + (env', [bndr']) <- newPolyBndrs dest_lvl env abs_vars [bndr_w_str] return (NonRec (TB bndr' dest_lvl) rhs', env') where - bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr - abs_vars = abstractVars dest_lvl env bind_fvs - dest_lvl = destLevel env bind_fvs (isFunction rhs) + bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr + abs_vars = abstractVars dest_lvl env bind_fvs + dest_lvl = destLevel env bind_fvs (isFunction rhs) mb_bot + mb_bot = exprBotStrictness_maybe (deAnnotate rhs) + bndr_w_str = annotateBotStr bndr mb_bot \end{code} \begin{code} lvlBind top_lvl ctxt_lvl env (AnnRec pairs) - | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe - = do rhss' <- mapM (lvlExpr ctxt_lvl env) rhss - return (Rec ([TB b ctxt_lvl | b <- bndrs] `zip` rhss'), env) - | null abs_vars = do (new_env, new_bndrs) <- cloneRecVars top_lvl env bndrs ctxt_lvl dest_lvl new_rhss <- mapM (lvlExpr ctxt_lvl new_env) rhss return (Rec ([TB b dest_lvl | b <- new_bndrs] `zip` new_rhss), new_env) - | isSingleton pairs && count isIdVar abs_vars > 1 + | isSingleton pairs && count isId abs_vars > 1 = do -- Special case for self recursion where there are -- several variables carried around: build a local loop: -- poly_f = \abs_vars. \lam_vars . letrec f = \lam_vars. rhs in f lam_vars @@ -568,7 +612,7 @@ lvlBind top_lvl ctxt_lvl env (AnnRec pairs) `minusVarSet` mkVarSet bndrs - dest_lvl = destLevel env bind_fvs (all isFunction rhss) + dest_lvl = destLevel env bind_fvs (all isFunction rhss) Nothing abs_vars = abstractVars dest_lvl env bind_fvs ---------------------------------------------------- @@ -605,7 +649,7 @@ lvlLamBndrs lvl bndrs [] bndrs where go old_lvl bumped_major rev_lvld_bndrs (bndr:bndrs) - | isIdVar bndr && -- Go to the next major level if this is a value binder, + | isId bndr && -- Go to the next major level if this is a value binder, not bumped_major && -- and we havn't already gone to the next level (one jump per group) not (isOneShotLambda bndr) -- and it isn't a one-shot lambda = go new_lvl True (TB bndr new_lvl : rev_lvld_bndrs) bndrs @@ -625,12 +669,14 @@ lvlLamBndrs lvl bndrs \begin{code} -- Destintion level is the max Id level of the expression -- (We'll abstract the type variables, if any.) -destLevel :: LevelEnv -> VarSet -> Bool -> Level -destLevel env fvs is_function +destLevel :: LevelEnv -> VarSet -> Bool -> Maybe (Arity, StrictSig) -> Level +destLevel env fvs is_function mb_bot + | Just {} <- mb_bot = tOP_LEVEL -- Send bottoming bindings to the top + -- regardless; see Note [Bottoming floats] | floatLams env - && is_function = tOP_LEVEL -- Send functions to top level; see + && is_function = tOP_LEVEL -- Send functions to top level; see -- the comments with isFunction - | otherwise = maxIdLevel env fvs + | otherwise = maxIdLevel env fvs isFunction :: CoreExprWithFVs -> Bool -- The idea here is that we want to float *functions* to @@ -647,7 +693,7 @@ isFunction :: CoreExprWithFVs -> Bool -- We may only want to do this if there are sufficiently few free -- variables. We certainly only want to do it for values, and not for -- constructors. So the simple thing is just to look for lambdas -isFunction (_, AnnLam b e) | isIdVar b = True +isFunction (_, AnnLam b e) | isId b = True | otherwise = isFunction e isFunction (_, AnnNote _ e) = isFunction e isFunction _ = False @@ -721,6 +767,12 @@ extendLvlEnv (float_lams, lvl_env, subst, id_env) prs -- incorrectly, because the SubstEnv was still lying around. Ouch! -- KSW 2000-07. +extendInScopeEnv :: LevelEnv -> Var -> LevelEnv +extendInScopeEnv (fl, le, subst, ids) v = (fl, le, extendInScope subst v, ids) + +extendInScopeEnvList :: LevelEnv -> [Var] -> LevelEnv +extendInScopeEnvList (fl, le, subst, ids) vs = (fl, le, extendInScopeList subst vs, ids) + -- extendCaseBndrLvlEnv adds the mapping case-bndr->scrut-var if it can -- (see point 4 of the module overview comment) extendCaseBndrLvlEnv :: LevelEnv -> Expr (TaggedBndr Level) -> Var -> Level @@ -765,10 +817,10 @@ maxIdLevel (_, lvl_env,_,id_env) var_set Nothing -> [in_var]) max_out out_var lvl - | isIdVar out_var = case lookupVarEnv lvl_env out_var of + | isId out_var = case lookupVarEnv lvl_env out_var of Just lvl' -> maxLvl lvl' lvl Nothing -> lvl - | otherwise = lvl -- Ignore tyvars in *maxIdLevel* + | otherwise = lvl -- Ignore tyvars in *maxIdLevel* lookupVar :: LevelEnv -> Id -> LevelledExpr lookupVar (_, _, _, id_env) v = case lookupVarEnv id_env v of @@ -808,7 +860,7 @@ abstractVars dest_lvl (_, lvl_env, _, id_env) fvs -- We are going to lambda-abstract, so nuke any IdInfo, -- and add the tyvars of the Id (if necessary) - zap v | isIdVar v = WARN( workerExists (idWorkerInfo v) || + zap v | isId v = WARN( isInlineRule (idUnfolding v) || not (isEmptySpecInfo (idSpecialisation v)), text "absVarsOf: discarding info on" <+> ppr v ) setIdInfo v vanillaIdInfo @@ -823,7 +875,7 @@ absVarsOf :: IdEnv ([Var], LevelledExpr) -> Var -> [Var] -- we must look in x's type -- And similarly if x is a coercion variable. absVarsOf id_env v - | isIdVar v = [av2 | av1 <- lookup_avs v + | isId v = [av2 | av1 <- lookup_avs v , av2 <- add_tyvars av1] | isCoVar v = add_tyvars v | otherwise = [v] @@ -851,27 +903,37 @@ newPolyBndrs dest_lvl env abs_vars bndrs = do let new_bndrs = zipWith mk_poly_bndr bndrs uniqs return (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs) where - mk_poly_bndr bndr uniq = transferPolyIdInfo bndr $ -- Note [transferPolyIdInfo] in Id.lhs + mk_poly_bndr bndr uniq = transferPolyIdInfo bndr abs_vars $ -- Note [transferPolyIdInfo] in Id.lhs mkSysLocal (mkFastString str) uniq poly_ty where str = "poly_" ++ occNameString (getOccName bndr) poly_ty = mkPiTypes abs_vars (idType bndr) -newLvlVar :: String - -> [CoreBndr] -> Type -- Abstract wrt these bndrs +newLvlVar :: [CoreBndr] -> Type -- Abstract wrt these bndrs + -> Maybe (Arity, StrictSig) -- Note [Bottoming floats] -> LvlM Id -newLvlVar str vars body_ty = do - uniq <- getUniqueM - return (mkSysLocal (mkFastString str) uniq (mkPiTypes vars body_ty)) +newLvlVar vars body_ty mb_bot + = do { uniq <- getUniqueM + ; return (mkLocalIdWithInfo (mk_name uniq) (mkPiTypes vars body_ty) info) } + where + mk_name uniq = mkSystemVarName uniq (mkFastString "lvl") + arity = count isId vars + info = case mb_bot of + Nothing -> vanillaIdInfo + Just (bot_arity, sig) -> vanillaIdInfo + `setArityInfo` (arity + bot_arity) + `setStrictnessInfo` Just (increaseStrictSigArity arity sig) -- The deeply tiresome thing is that we have to apply the substitution -- to the rules inside each Id. Grr. But it matters. cloneVar :: TopLevelFlag -> LevelEnv -> Id -> Level -> Level -> LvlM (LevelEnv, Id) cloneVar TopLevel env v _ _ - = return (env, v) -- Don't clone top level things + = return (extendInScopeEnv env v, v) -- Don't clone top level things + -- But do extend the in-scope env, to satisfy the in-scope invariant + cloneVar NotTopLevel env@(_,_,subst,_) v ctxt_lvl dest_lvl - = ASSERT( isIdVar v ) do + = ASSERT( isId v ) do us <- getUniqueSupplyM let (subst', v1) = cloneIdBndr subst us v @@ -881,9 +943,9 @@ cloneVar NotTopLevel env@(_,_,subst,_) v ctxt_lvl dest_lvl cloneRecVars :: TopLevelFlag -> LevelEnv -> [Id] -> Level -> Level -> LvlM (LevelEnv, [Id]) cloneRecVars TopLevel env vs _ _ - = return (env, vs) -- Don't clone top level things + = return (extendInScopeEnvList env vs, vs) -- Don't clone top level things cloneRecVars NotTopLevel env@(_,_,subst,_) vs ctxt_lvl dest_lvl - = ASSERT( all isIdVar vs ) do + = ASSERT( all isId vs ) do us <- getUniqueSupplyM let (subst', vs1) = cloneRecIdBndrs subst us vs