X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fspecialise%2FSpecConstr.lhs;h=f366cd7764ae9d0a3301d279aee1156c0a77ea53;hb=2d7794dcb47f8d157d284912dbff3f65dedc0a2b;hp=a52de103c3895bd1574ef3370a8edba20890427f;hpb=9bcaaaaa59acff95886ad3675677e58c43106bd2;p=ghc-hetmet.git diff --git a/compiler/specialise/SpecConstr.lhs b/compiler/specialise/SpecConstr.lhs index a52de10..f366cd7 100644 --- a/compiler/specialise/SpecConstr.lhs +++ b/compiler/specialise/SpecConstr.lhs @@ -11,7 +11,7 @@ -- for details module SpecConstr( - specConstrProgram + specConstrProgram, SpecConstrAnnotation(..) ) where #include "HsVersions.h" @@ -20,35 +20,40 @@ import CoreSyn import CoreSubst import CoreUtils import CoreUnfold ( couldBeSmallEnoughToInline ) -import CoreLint ( showPass, endPass ) import CoreFVs ( exprsFreeVars ) -import CoreTidy ( tidyRules ) -import PprCore ( pprRules ) +import CoreMonad +import HscTypes ( ModGuts(..) ) import WwLib ( mkWorkerArgs ) -import DataCon ( dataConRepArity, dataConUnivTyVars ) +import DataCon ( dataConTyCon, dataConRepArity, dataConUnivTyVars ) +import TyCon ( TyCon ) +import Literal ( literalType ) import Coercion +import Rules import Type hiding( substTy ) -import Id ( Id, idName, idType, isDataConWorkId_maybe, idArity, - mkUserLocal, mkSysLocal, idUnfolding, isLocalId ) +import Id +import MkId ( mkImpossibleExpr ) import Var import VarEnv import VarSet import Name -import Rules ( addIdSpecialisations, mkLocalRule, rulesOfBinds ) -import OccName ( mkSpecOcc ) -import ErrUtils ( dumpIfSet_dyn ) -import DynFlags ( DynFlags(..), DynFlag(..) ) +import DynFlags ( DynFlags(..) ) +import StaticFlags ( opt_PprStyle_Debug ) import StaticFlags ( opt_SpecInlineJoinPoints ) import BasicTypes ( Activation(..) ) import Maybes ( orElse, catMaybes, isJust, isNothing ) +import NewDemand +import DmdAnal ( both ) +import Serialized ( deserializeWithData ) import Util -import List ( nubBy, partition ) import UniqSupply import Outputable import FastString import UniqFM +import qualified LazyUniqFM as L import MonadUtils import Control.Monad ( zipWithM ) +import Data.List +import Data.Data ( Data, Typeable ) \end{code} ----------------------------------------------------- @@ -369,6 +374,19 @@ specialising the loops arising from stream fusion, for example in NDP where we were getting literally hundreds of (mostly unused) specialisations of a local function. +Note [Do not specialise diverging functions] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Specialising a function that just diverges is a waste of code. +Furthermore, it broke GHC (simpl014) thus: + {-# STR Sb #-} + f = \x. case x of (a,b) -> f x +If we specialise f we get + f = \x. case x of (a,b) -> fspec a b +But fspec doesn't have decent strictnes info. As it happened, +(f x) :: IO t, so the state hack applied and we eta expanded fspec, +and hence f. But now f's strictness is less than its arity, which +breaks an invariant. + ----------------------------------------------------- Stuff not yet handled ----------------------------------------------------- @@ -444,7 +462,18 @@ But perhaps the first one isn't good. After all, we know that tpl_B2 is a T (I# x) really, because T is strict and Int has one constructor. (We can't unbox the strict fields, becuase T is polymorphic!) +%************************************************************************ +%* * +\subsection{Annotations} +%* * +%************************************************************************ + +Annotating a type with NoSpecConstr will make SpecConstr not specialise +for arguments of that type. +\begin{code} +data SpecConstrAnnotation = NoSpecConstr deriving( Data, Typeable ) +\end{code} %************************************************************************ %* * @@ -453,20 +482,14 @@ unbox the strict fields, becuase T is polymorphic!) %************************************************************************ \begin{code} -specConstrProgram :: DynFlags -> UniqSupply -> [CoreBind] -> IO [CoreBind] -specConstrProgram dflags us binds +specConstrProgram :: ModGuts -> CoreM ModGuts +specConstrProgram guts = do - showPass dflags "SpecConstr" - - let (binds', _) = initUs us (go (initScEnv dflags) binds) - - endPass dflags "SpecConstr" Opt_D_dump_spec binds' - - dumpIfSet_dyn dflags Opt_D_dump_rules "Top-level specialisations" - (withPprStyle defaultUserStyle $ - pprRules (tidyRules emptyTidyEnv (rulesOfBinds binds'))) - - return binds' + dflags <- getDynFlags + us <- getUniqueSupplyM + annos <- deserializeAnnotations deserializeWithData + let binds' = fst $ initUs us (go (initScEnv dflags annos) (mg_binds guts)) + return (guts { mg_binds = binds' }) where go _ [] = return [] go env (bind:binds) = do (env', bind') <- scTopBind env bind @@ -492,9 +515,11 @@ data ScEnv = SCE { sc_size :: Maybe Int, -- Size threshold -- Binds interesting non-top-level variables -- Domain is OutVars (*after* applying the substitution) - sc_vals :: ValueEnv + sc_vals :: ValueEnv, -- Domain is OutIds (*after* applying the substitution) -- Used even for top-level bindings (but not imported ones) + + sc_annotations :: L.UniqFM SpecConstrAnnotation } --------------------- @@ -518,13 +543,14 @@ instance Outputable Value where ppr LambdaVal = ptext (sLit "") --------------------- -initScEnv :: DynFlags -> ScEnv -initScEnv dflags +initScEnv :: DynFlags -> L.UniqFM [SpecConstrAnnotation] -> ScEnv +initScEnv dflags annos = SCE { sc_size = specConstrThreshold dflags, sc_count = specConstrCount dflags, sc_subst = emptySubst, sc_how_bound = emptyVarEnv, - sc_vals = emptyVarEnv } + sc_vals = emptyVarEnv, + sc_annotations = L.mapUFM head $ L.filterUFM (not . null) annos } data HowBound = RecFun -- These are the recursive functions for which -- we seek interesting call patterns @@ -593,17 +619,28 @@ extendValEnv :: ScEnv -> Id -> Maybe Value -> ScEnv extendValEnv env _ Nothing = env extendValEnv env id (Just cv) = env { sc_vals = extendVarEnv (sc_vals env) id cv } -extendCaseBndrs :: ScEnv -> CoreExpr -> Id -> AltCon -> [Var] -> ScEnv +extendCaseBndrs :: ScEnv -> Id -> AltCon -> [Var] -> (ScEnv, [Var]) -- When we encounter -- case scrut of b -- C x y -> ... --- we want to bind b, and perhaps scrut too, to (C x y) --- NB: Extends only the sc_vals part of the envt -extendCaseBndrs env scrut case_bndr con alt_bndrs - = case scrut of - Var v -> extendValEnv env1 v cval - _other -> env1 +-- we want to bind b, to (C x y) +-- NB1: Extends only the sc_vals part of the envt +-- NB2: Kill the dead-ness info on the pattern binders x,y, since +-- they are potentially made alive by the [b -> C x y] binding +extendCaseBndrs env case_bndr con alt_bndrs + | isDeadBinder case_bndr + = (env, alt_bndrs) + | otherwise + = (env1, map zap alt_bndrs) + -- NB: We used to bind v too, if scrut = (Var v); but + -- the simplifer has already done this so it seems + -- redundant to do so here + -- case scrut of + -- Var v -> extendValEnv env1 v cval + -- _other -> env1 where + zap v | isTyVar v = v -- See NB2 above + | otherwise = zapIdOccInfo v env1 = extendValEnv env case_bndr cval cval = case con of DEFAULT -> Nothing @@ -612,6 +649,23 @@ extendCaseBndrs env scrut case_bndr con alt_bndrs where vanilla_args = map Type (tyConAppArgs (idType case_bndr)) ++ varsToCoreExprs alt_bndrs + +ignoreTyCon :: ScEnv -> TyCon -> Bool +ignoreTyCon env tycon + = case L.lookupUFM (sc_annotations env) tycon of + Just NoSpecConstr -> True + _ -> False + +ignoreType :: ScEnv -> Type -> Bool +ignoreType env ty + = case splitTyConApp_maybe ty of + Just (tycon, _) -> ignoreTyCon env tycon + _ -> False + +ignoreAltCon :: ScEnv -> AltCon -> Bool +ignoreAltCon env (DataAlt dc) = ignoreTyCon env (dataConTyCon dc) +ignoreAltCon env (LitAlt lit) = ignoreType env (literalType lit) +ignoreAltCon _ DEFAULT = True \end{code} @@ -770,7 +824,8 @@ scExpr' env (Case scrut b ty alts) where sc_con_app con args scrut' -- Known constructor; simplify = do { let (_, bs, rhs) = findAlt con alts - alt_env' = extendScSubstList env ((b,scrut') : bs `zip` trimConArgs con args) + `orElse` (DEFAULT, [], mkImpossibleExpr (coreAltsType alts)) + alt_env' = extendScSubstList env ((b,scrut') : bs `zip` trimConArgs con args) ; scExpr alt_env' rhs } sc_vanilla scrut_usg scrut' -- Normal case @@ -790,15 +845,15 @@ scExpr' env (Case scrut b ty alts) ; return (alt_usg `combineUsage` scrut_usg', Case scrut' b' (scSubstTy env ty) alts') } - sc_alt env scrut' b' (con,bs,rhs) - = do { let (env1, bs') = extendBndrsWith RecArg env bs - env2 = extendCaseBndrs env1 scrut' b' con bs' + sc_alt env _scrut' b' (con,bs,rhs) + = do { let (env1, bs1) = extendBndrsWith RecArg env bs + (env2, bs2) = extendCaseBndrs env1 b' con bs1 ; (usg,rhs') <- scExpr env2 rhs - ; let (usg', arg_occs) = lookupOccs usg bs' + ; let (usg', arg_occs) = lookupOccs usg bs2 scrut_occ = case con of DataAlt dc -> ScrutOcc (unitUFM dc arg_occs) _ -> ScrutOcc emptyUFM - ; return (usg', scrut_occ, (con,bs',rhs')) } + ; return (usg', scrut_occ, (con, bs2, rhs')) } scExpr' env (Let (NonRec bndr rhs) body) | isTyVar bndr -- Type-lets may be created by doBeta @@ -1011,8 +1066,9 @@ specialise specialise env bind_calls (fn, arg_bndrs, body, arg_occs) spec_info@(SI specs spec_count mb_unspec) - | notNull arg_bndrs, -- Only specialise functions - Just all_calls <- lookupVarEnv bind_calls fn + | not (isBottomingId fn) -- Note [Do not specialise diverging functions] + , notNull arg_bndrs -- Only specialise functions + , Just all_calls <- lookupVarEnv bind_calls fn = do { (boring_call, pats) <- callsToPats env specs arg_occs all_calls -- ; pprTrace "specialise" (vcat [ppr fn <+> ppr arg_occs, -- text "calls" <+> ppr all_calls, @@ -1024,10 +1080,14 @@ specialise env bind_calls (fn, arg_bndrs, body, arg_occs) ; let spec_count' = length pats + spec_count ; case sc_count env of Just max | spec_count' > max - -> pprTrace "SpecConstr: too many specialisations for one function (see -fspec-constr-count):" - (vcat [ptext (sLit "Function:") <+> ppr fn, - ptext (sLit "Specialisations:") <+> ppr (pats ++ [p | OS p _ _ _ <- specs])]) - return (nullUsage, spec_info) + -> WARN( True, msg ) return (nullUsage, spec_info) + where + msg = vcat [ sep [ ptext (sLit "SpecConstr: specialisation of") <+> quotes (ppr fn) + , nest 2 (ptext (sLit "limited by bound of")) <+> int max ] + , ptext (sLit "Use -fspec-constr-count=n to set the bound") + , extra ] + extra | not opt_PprStyle_Debug = ptext (sLit "Use -dppr-debug to see specialisations") + | otherwise = ptext (sLit "Specialisations:") <+> ppr (pats ++ [p | OS p _ _ _ <- specs]) _normal_case -> do { @@ -1096,12 +1156,37 @@ spec_one env fn arg_bndrs body (call_pat@(qvars, pats), rule_number) spec_occ = mkSpecOcc (nameOccName fn_name) rule_name = mkFastString ("SC:" ++ showSDoc (ppr fn <> int rule_number)) spec_rhs = mkLams spec_lam_args spec_body + spec_str = calcSpecStrictness fn spec_lam_args pats spec_id = mkUserLocal spec_occ spec_uniq (mkPiTypes spec_lam_args body_ty) fn_loc + `setIdNewStrictness` spec_str -- See Note [Transfer strictness] + `setIdArity` count isId spec_lam_args body_ty = exprType spec_body rule_rhs = mkVarApps (Var spec_id) spec_call_args rule = mkLocalRule rule_name specConstrActivation fn_name qvars pats rule_rhs ; return (spec_usg, OS call_pat rule spec_id spec_rhs) } +calcSpecStrictness :: Id -- The original function + -> [Var] -> [CoreExpr] -- Call pattern + -> StrictSig -- Strictness of specialised thing +-- See Note [Transfer strictness] +calcSpecStrictness fn qvars pats + = StrictSig (mkTopDmdType spec_dmds TopRes) + where + spec_dmds = [ lookupVarEnv dmd_env qv `orElse` lazyDmd | qv <- qvars, isId qv ] + StrictSig (DmdType _ dmds _) = idNewStrictness fn + + dmd_env = go emptyVarEnv dmds pats + + go env ds (Type {} : pats) = go env ds pats + go env (d:ds) (pat : pats) = go (go_one env d pat) ds pats + go env _ _ = env + + go_one env d (Var v) = extendVarEnv_C both env v d + go_one env (Box d) e = go_one env d e + go_one env (Eval (Prod ds)) e + | (Var _, args) <- collectArgs e = go env ds args + go_one env _ _ = env + -- In which phase should the specialise-constructor rules be active? -- Originally I made them always-active, but Manuel found that -- this defeated some clever user-written rules. So Plan B @@ -1114,6 +1199,23 @@ specConstrActivation :: Activation specConstrActivation = ActiveAfter 0 -- Baked in; see comments above \end{code} +Note [Transfer strictness] +~~~~~~~~~~~~~~~~~~~~~~~~~~ +We must transfer strictness information from the original function to +the specialised one. Suppose, for example + + f has strictness SS + and a RULE f (a:as) b = f_spec a as b + +Now we want f_spec to have strictess LLS, otherwise we'll use call-by-need +when calling f_spec instead of call-by-value. And that can result in +unbounded worsening in space (cf the classic foldl vs foldl') + +See Trac #3437 for a good example. + +The function calcSpecStrictness performs the calculation. + + %************************************************************************ %* * \subsection{Argument analysis} @@ -1153,7 +1255,7 @@ callToPats env bndr_occs (con_env, args) = return Nothing | otherwise = do { let in_scope = substInScope (sc_subst env) - ; prs <- argsToPats in_scope con_env (args `zip` bndr_occs) + ; prs <- argsToPats env in_scope con_env (args `zip` bndr_occs) ; let (interesting_s, pats) = unzip prs pat_fvs = varSetElems (exprsFreeVars pats) qvars = filterOut (`elemInScopeSet` in_scope) pat_fvs @@ -1177,7 +1279,8 @@ callToPats env bndr_occs (con_env, args) -- placeholder variables. For example: -- C a (D (f x) (g y)) ==> C p1 (D p2 p3) -argToPat :: InScopeSet -- What's in scope at the fn defn site +argToPat :: ScEnv + -> InScopeSet -- What's in scope at the fn defn site -> ValueEnv -- ValueEnv at the call site -> CoreArg -- A call arg (or component thereof) -> ArgOcc @@ -1192,11 +1295,11 @@ argToPat :: InScopeSet -- What's in scope at the fn defn site -- lvl7 --> (True, lvl7) if lvl7 is bound -- somewhere further out -argToPat _in_scope _val_env arg@(Type {}) _arg_occ +argToPat _env _in_scope _val_env arg@(Type {}) _arg_occ = return (False, arg) -argToPat in_scope val_env (Note _ arg) arg_occ - = argToPat in_scope val_env arg arg_occ +argToPat env in_scope val_env (Note _ arg) arg_occ + = argToPat env in_scope val_env arg arg_occ -- Note [Notes in call patterns] -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- Ignore Notes. In particular, we want to ignore any InlineMe notes @@ -1204,16 +1307,16 @@ argToPat in_scope val_env (Note _ arg) arg_occ -- ride roughshod over them all for now. --- See Note [Notes in RULE matching] in Rules -argToPat in_scope val_env (Let _ arg) arg_occ - = argToPat in_scope val_env arg arg_occ +argToPat env in_scope val_env (Let _ arg) arg_occ + = argToPat env in_scope val_env arg arg_occ -- Look through let expressions -- e.g. f (let v = rhs in \y -> ...v...) -- Here we can specialise for f (\y -> ...) -- because the rule-matcher will look through the let. -argToPat in_scope val_env (Cast arg co) arg_occ - = do { (interesting, arg') <- argToPat in_scope val_env arg arg_occ - ; let (ty1,ty2) = coercionKind co +argToPat env in_scope val_env (Cast arg co) arg_occ + | not (ignoreType env ty2) + = do { (interesting, arg') <- argToPat env in_scope val_env arg arg_occ ; if not interesting then wildCardPat ty2 else do @@ -1222,6 +1325,10 @@ argToPat in_scope val_env (Cast arg co) arg_occ ; let co_name = mkSysTvName uniq (fsLit "sg") co_var = mkCoVar co_name (mkCoKind ty1 ty2) ; return (interesting, Cast arg' (mkTyVarTy co_var)) } } + where + (ty1, ty2) = coercionKind co + + {- Disabling lambda specialisation for now It's fragile, and the spec_loop can be infinite @@ -1237,15 +1344,16 @@ argToPat in_scope val_env arg arg_occ -- Check for a constructor application -- NB: this *precedes* the Var case, so that we catch nullary constrs -argToPat in_scope val_env arg arg_occ +argToPat env in_scope val_env arg arg_occ | Just (ConVal dc args) <- isValue val_env arg + , not (ignoreAltCon env dc) , case arg_occ of ScrutOcc _ -> True -- Used only by case scrutinee BothOcc -> case arg of -- Used elsewhere App {} -> True -- see Note [Reboxing] _other -> False _other -> False -- No point; the arg is not decomposed - = do { args' <- argsToPats in_scope val_env (args `zip` conArgOccs arg_occ dc) + = do { args' <- argsToPats env in_scope val_env (args `zip` conArgOccs arg_occ dc) ; return (True, mk_con_app dc (map snd args')) } -- Check if the argument is a variable that @@ -1253,9 +1361,10 @@ argToPat in_scope val_env arg arg_occ -- It's worth specialising on this if -- (a) it's used in an interesting way in the body -- (b) we know what its value is -argToPat in_scope val_env (Var v) arg_occ +argToPat env in_scope val_env (Var v) arg_occ | case arg_occ of { UnkOcc -> False; _other -> True }, -- (a) - is_value -- (b) + is_value, -- (b) + not (ignoreType env (varType v)) = return (True, Var v) where is_value @@ -1284,7 +1393,7 @@ argToPat in_scope val_env (Var v) arg_occ -- We don't want to specialise for that *particular* x,y -- The default case: make a wild-card -argToPat _in_scope _val_env arg _arg_occ +argToPat _env _in_scope _val_env arg _arg_occ = wildCardPat (exprType arg) wildCardPat :: Type -> UniqSM (Bool, CoreArg) @@ -1292,13 +1401,13 @@ wildCardPat ty = do { uniq <- getUniqueUs ; let id = mkSysLocal (fsLit "sc") uniq ty ; return (False, Var id) } -argsToPats :: InScopeSet -> ValueEnv +argsToPats :: ScEnv -> InScopeSet -> ValueEnv -> [(CoreArg, ArgOcc)] -> UniqSM [(Bool, CoreArg)] -argsToPats in_scope val_env args +argsToPats env in_scope val_env args = mapM do_one args where - do_one (arg,occ) = argToPat in_scope val_env arg occ + do_one (arg,occ) = argToPat env in_scope val_env arg occ \end{code}