X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Fstranal%2FDmdAnal.lhs;h=c5cfb7b4bdedde682e5b88669b8305dfef7c07ab;hb=95c13506a9988cfe613618ef5c76fe95f4048d22;hp=5f80ced37f9c05955896b965f912d4d07c8e3a69;hpb=7ca7d77a8ee046d26930792edd1a7b2b09a7870b;p=ghc-hetmet.git diff --git a/ghc/compiler/stranal/DmdAnal.lhs b/ghc/compiler/stranal/DmdAnal.lhs index 5f80ced..c5cfb7b 100644 --- a/ghc/compiler/stranal/DmdAnal.lhs +++ b/ghc/compiler/stranal/DmdAnal.lhs @@ -7,33 +7,46 @@ ----------------- \begin{code} -module DmdAnal ( dmdAnalPgm ) where +module DmdAnal ( dmdAnalPgm, dmdAnalTopRhs, + both {- needed by WwLib -} + ) where #include "HsVersions.h" -import CmdLineOpts ( DynFlags, DynFlag(..), opt_MaxWorkerArgs ) +import DynFlags ( DynFlags, DynFlag(..) ) +import StaticFlags ( opt_MaxWorkerArgs ) import NewDemand -- All of it import CoreSyn -import CoreUtils ( exprIsValue, exprArity ) +import PprCore +import CoreUtils ( exprIsHNF, exprIsTrivial, exprArity ) import DataCon ( dataConTyCon ) import TyCon ( isProductTyCon, isRecursiveTyCon ) -import Id ( Id, idType, idInfo, idArity, idCprInfo, idDemandInfo, - modifyIdInfo, isDataConId, isImplicitId, isGlobalId, - idNewStrictness, idNewStrictness_maybe, getNewStrictness, setIdNewStrictness, - idNewDemandInfo, setIdNewDemandInfo, newStrictnessFromOld ) -import IdInfo ( newDemand ) +import Id ( Id, idType, idInlinePragma, + isDataConWorkId, isGlobalId, idArity, +#ifdef OLD_STRICTNESS + idDemandInfo, idStrictness, idCprInfo, idName, +#endif + idNewStrictness, idNewStrictness_maybe, + setIdNewStrictness, idNewDemandInfo, + idNewDemandInfo_maybe, + setIdNewDemandInfo + ) +#ifdef OLD_STRICTNESS +import IdInfo ( newStrictnessFromOld, newDemand ) +#endif import Var ( Var ) import VarEnv +import TysWiredIn ( unboxedPairDataCon ) +import TysPrim ( realWorldStatePrimTy ) import UniqFM ( plusUFM_C, addToUFM_Directly, lookupUFM_Directly, keysUFM, minusUFM, ufmToList, filterUFM ) -import Type ( isUnLiftedType ) +import Type ( isUnLiftedType, coreEqType ) import CoreLint ( showPass, endPass ) -import ErrUtils ( dumpIfSet_dyn ) -import Util ( mapAndUnzip, mapAccumL, mapAccumR, zipWithEqual ) -import BasicTypes ( Arity, TopLevelFlag(..), isTopLevel ) +import Util ( mapAndUnzip, mapAccumL, mapAccumR, lengthIs ) +import BasicTypes ( Arity, TopLevelFlag(..), isTopLevel, isNeverActive, + RecFlag(..), isRec ) import Maybes ( orElse, expectJust ) import Outputable -import FastTypes \end{code} To think about @@ -43,10 +56,6 @@ To think about * Consider f x = x+1 `fatbar` error (show x) We'd like to unbox x, even if that means reboxing it in the error case. -\begin{code} -instance Outputable TopLevelFlag where - ppr flag = empty -\end{code} %************************************************************************ %* * @@ -59,12 +68,14 @@ dmdAnalPgm :: DynFlags -> [CoreBind] -> IO [CoreBind] dmdAnalPgm dflags binds = do { showPass dflags "Demand analysis" ; - let { binds_plus_dmds = do_prog binds ; - dmd_changes = get_changes binds_plus_dmds } ; + let { binds_plus_dmds = do_prog binds } ; + endPass dflags "Demand analysis" Opt_D_dump_stranal binds_plus_dmds ; -#ifdef DEBUG - -- Only if DEBUG is on, because only then is the old strictness analyser run +#ifdef OLD_STRICTNESS + -- Only if OLD_STRICTNESS is on, because only then is the old + -- strictness analyser run + let { dmd_changes = get_changes binds_plus_dmds } ; printDump (text "Changes in demands" $$ dmd_changes) ; #endif return binds_plus_dmds @@ -77,21 +88,43 @@ dmdAnalTopBind :: SigEnv -> CoreBind -> (SigEnv, CoreBind) dmdAnalTopBind sigs (NonRec id rhs) - | isImplicitId id -- Don't touch the info on constructors, selectors etc - = (sigs, NonRec id rhs) -- It's pre-computed in MkId.lhs - | otherwise = let - (sigs', _, (id', rhs')) = downRhs TopLevel sigs (id, rhs) + ( _, _, (_, rhs1)) = dmdAnalRhs TopLevel NonRecursive sigs (id, rhs) + (sigs2, _, (id2, rhs2)) = dmdAnalRhs TopLevel NonRecursive sigs (id, rhs1) + -- Do two passes to improve CPR information + -- See comments with ignore_cpr_info in mk_sig_ty + -- and with extendSigsWithLam in - (sigs', NonRec id' rhs') + (sigs2, NonRec id2 rhs2) dmdAnalTopBind sigs (Rec pairs) = let (sigs', _, pairs') = dmdFix TopLevel sigs pairs + -- We get two iterations automatically + -- c.f. the NonRec case above in (sigs', Rec pairs') \end{code} +\begin{code} +dmdAnalTopRhs :: CoreExpr -> (StrictSig, CoreExpr) +-- Analyse the RHS and return +-- a) appropriate strictness info +-- b) the unfolding (decorated with stricntess info) +dmdAnalTopRhs rhs + = (sig, rhs2) + where + call_dmd = vanillaCall (exprArity rhs) + (_, rhs1) = dmdAnal emptySigEnv call_dmd rhs + (rhs_ty, rhs2) = dmdAnal emptySigEnv call_dmd rhs1 + sig = mkTopSigTy rhs rhs_ty + -- Do two passes; see notes with extendSigsWithLam + -- Otherwise we get bogus CPR info for constructors like + -- newtype T a = MkT a + -- The constructor looks like (\x::T a -> x), modulo the coerce + -- extendSigsWithLam will optimistically give x a CPR tag the + -- first time, which is wrong in the end. +\end{code} %************************************************************************ %* * @@ -104,10 +137,12 @@ dmdAnal :: SigEnv -> Demand -> CoreExpr -> (DmdType, CoreExpr) dmdAnal sigs Abs e = (topDmdType, e) -dmdAnal sigs Lazy e = let - (res_ty, e') = dmdAnal sigs Eval e - in - (deferType res_ty, e') +dmdAnal sigs dmd e + | not (isStrictDmd dmd) + = let + (res_ty, e') = dmdAnal sigs evalDmd e + in + (deferType res_ty, e') -- It's important not to analyse e with a lazy demand because -- a) When we encounter case s of (a,b) -> -- we demand s with U(d1d2)... but if the overall demand is lazy @@ -118,6 +153,9 @@ dmdAnal sigs Lazy e = let -- We still want to mark x as demanded, because it will be when we -- enter the let. If we analyse f's arg with a Lazy demand, we'll -- just mark x as Lazy + -- c) The application rule wouldn't be right either + -- Evaluating (f x) in a L demand does *not* cause + -- evaluation of f in a C(L) demand! dmdAnal sigs dmd (Lit lit) @@ -131,18 +169,20 @@ dmdAnal sigs dmd (Note n e) where (dmd_ty, e') = dmdAnal sigs dmd' e dmd' = case n of - Coerce _ _ -> Eval -- This coerce usually arises from a recursive - other -> dmd -- newtype, and we don't want to look inside them - -- for exactly the same reason that we don't look - -- inside recursive products -- we might not reach - -- a fixpoint. So revert to a vanilla Eval demand + Coerce _ _ -> evalDmd -- This coerce usually arises from a recursive + other -> dmd -- newtype, and we don't want to look inside them + -- for exactly the same reason that we don't look + -- inside recursive products -- we might not reach + -- a fixpoint. So revert to a vanilla Eval demand dmdAnal sigs dmd (App fun (Type ty)) = (fun_ty, App fun' (Type ty)) where (fun_ty, fun') = dmdAnal sigs dmd fun -dmdAnal sigs dmd (App fun arg) -- Non-type arguments +-- Lots of the other code is there to make this +-- beautiful, compositional, application rule :-) +dmdAnal sigs dmd e@(App fun arg) -- Non-type arguments = let -- [Type arg handled above] (fun_ty, fun') = dmdAnal sigs (Call dmd) fun (arg_ty, arg') = dmdAnal sigs arg_dmd arg @@ -159,61 +199,95 @@ dmdAnal sigs dmd (Lam var body) | Call body_dmd <- dmd -- A call demand: good! = let - (body_ty, body') = dmdAnal sigs body_dmd body + sigs' = extendSigsWithLam sigs var + (body_ty, body') = dmdAnal sigs' body_dmd body (lam_ty, var') = annotateLamIdBndr body_ty var in (lam_ty, Lam var' body') | otherwise -- Not enough demand on the lambda; but do the body = let -- anyway to annotate it and gather free var info - (body_ty, body') = dmdAnal sigs Eval body + (body_ty, body') = dmdAnal sigs evalDmd body (lam_ty, var') = annotateLamIdBndr body_ty var in (deferType lam_ty, Lam var' body') -dmdAnal sigs dmd (Case scrut case_bndr [alt@(DataAlt dc,bndrs,rhs)]) +dmdAnal sigs dmd (Case scrut case_bndr ty [alt@(DataAlt dc,bndrs,rhs)]) | let tycon = dataConTyCon dc, isProductTyCon tycon, not (isRecursiveTyCon tycon) = let - bndr_ids = filter isId bndrs - (alt_ty, alt') = dmdAnalAlt sigs dmd alt - (alt_ty1, case_bndr') = annotateBndr alt_ty case_bndr - (_, bndrs', _) = alt' - - -- Figure out whether the case binder is used, and use - -- that to set the keepity of the demand. This is utterly essential. + sigs_alt = extendSigEnv NotTopLevel sigs case_bndr case_bndr_sig + (alt_ty, alt') = dmdAnalAlt sigs_alt dmd alt + (alt_ty1, case_bndr') = annotateBndr alt_ty case_bndr + (_, bndrs', _) = alt' + case_bndr_sig = cprSig + -- Inside the alternative, the case binder has the CPR property. + -- Meaning that a case on it will successfully cancel. + -- Example: + -- f True x = case x of y { I# x' -> if x' ==# 3 then y else I# 8 } + -- f False x = I# 3 + -- + -- We want f to have the CPR property: + -- f b x = case fw b x of { r -> I# r } + -- fw True x = case x of y { I# x' -> if x' ==# 3 then x' else 8 } + -- fw False x = 3 + + -- Figure out whether the demand on the case binder is used, and use + -- that to set the scrut_dmd. This is utterly essential. -- Consider f x = case x of y { (a,b) -> k y a } -- If we just take scrut_demand = U(L,A), then we won't pass x to the -- worker, so the worker will rebuild -- x = (a, absent-error) -- and that'll crash. - dead_case_bndr = isAbsentDmd (idNewDemandInfo case_bndr') - keepity | dead_case_bndr = Drop - | otherwise = Keep - - scrut_dmd = Seq keepity Now [idNewDemandInfo b | b <- bndrs', isId b] - (scrut_ty, scrut') = dmdAnal sigs scrut_dmd scrut + -- So at one stage I had: + -- dead_case_bndr = isAbsentDmd (idNewDemandInfo case_bndr') + -- keepity | dead_case_bndr = Drop + -- | otherwise = Keep + -- + -- But then consider + -- case x of y { (a,b) -> h y + a } + -- where h : U(LL) -> T + -- The above code would compute a Keep for x, since y is not Abs, which is silly + -- The insight is, of course, that a demand on y is a demand on the + -- scrutinee, so we need to `both` it with the scrut demand + + scrut_dmd = Eval (Prod [idNewDemandInfo b | b <- bndrs', isId b]) + `both` + idNewDemandInfo case_bndr' + + (scrut_ty, scrut') = dmdAnal sigs scrut_dmd scrut in - (alt_ty1 `bothType` scrut_ty, Case scrut' case_bndr' [alt']) + (alt_ty1 `bothType` scrut_ty, Case scrut' case_bndr' ty [alt']) -dmdAnal sigs dmd (Case scrut case_bndr alts) +dmdAnal sigs dmd (Case scrut case_bndr ty alts) = let (alt_tys, alts') = mapAndUnzip (dmdAnalAlt sigs dmd) alts - (scrut_ty, scrut') = dmdAnal sigs Eval scrut + (scrut_ty, scrut') = dmdAnal sigs evalDmd scrut (alt_ty, case_bndr') = annotateBndr (foldr1 lubType alt_tys) case_bndr in -- pprTrace "dmdAnal:Case" (ppr alts $$ ppr alt_tys) - (alt_ty `bothType` scrut_ty, Case scrut' case_bndr' alts') + (alt_ty `bothType` scrut_ty, Case scrut' case_bndr' ty alts') dmdAnal sigs dmd (Let (NonRec id rhs) body) = let - (sigs', lazy_fv, (id1, rhs')) = downRhs NotTopLevel sigs (id, rhs) + (sigs', lazy_fv, (id1, rhs')) = dmdAnalRhs NotTopLevel NonRecursive sigs (id, rhs) (body_ty, body') = dmdAnal sigs' dmd body (body_ty1, id2) = annotateBndr body_ty id1 body_ty2 = addLazyFVs body_ty1 lazy_fv in --- pprTrace "dmdLet" (ppr id <+> ppr (sig,rhs_env)) + -- If the actual demand is better than the vanilla call + -- demand, you might think that we might do better to re-analyse + -- the RHS with the stronger demand. + -- But (a) That seldom happens, because it means that *every* path in + -- the body of the let has to use that stronger demand + -- (b) It often happens temporarily in when fixpointing, because + -- the recursive function at first seems to place a massive demand. + -- But we don't want to go to extra work when the function will + -- probably iterate to something less demanding. + -- In practice, all the times the actual demand on id2 is more than + -- the vanilla call demand seem to be due to (b). So we don't + -- bother to re-analyse the RHS. (body_ty2, Let (NonRec id2 rhs') body') dmdAnal sigs dmd (Let (Rec pairs) body) @@ -238,8 +312,30 @@ dmdAnalAlt sigs dmd (con,bndrs,rhs) = let (rhs_ty, rhs') = dmdAnal sigs dmd rhs (alt_ty, bndrs') = annotateBndrs rhs_ty bndrs - in - (alt_ty, (con, bndrs', rhs')) + final_alt_ty | io_hack_reqd = alt_ty `lubType` topDmdType + | otherwise = alt_ty + + -- There's a hack here for I/O operations. Consider + -- case foo x s of { (# s, r #) -> y } + -- Is this strict in 'y'. Normally yes, but what if 'foo' is an I/O + -- operation that simply terminates the program (not in an erroneous way)? + -- In that case we should not evaluate y before the call to 'foo'. + -- Hackish solution: spot the IO-like situation and add a virtual branch, + -- as if we had + -- case foo x s of + -- (# s, r #) -> y + -- other -> return () + -- So the 'y' isn't necessarily going to be evaluated + -- + -- A more complete example where this shows up is: + -- do { let len = ; + -- ; when (...) (exitWith ExitSuccess) + -- ; print len } + + io_hack_reqd = con == DataAlt unboxedPairDataCon && + idType (head bndrs) `coreEqType` realWorldStatePrimTy + in + (final_alt_ty, (con, bndrs', rhs')) \end{code} %************************************************************************ @@ -255,29 +351,38 @@ dmdFix :: TopLevelFlag -> (SigEnv, DmdEnv, [(Id,CoreExpr)]) -- Binders annotated with stricness info -dmdFix top_lvl sigs pairs - = loop 1 initial_sigs pairs +dmdFix top_lvl sigs orig_pairs + = loop 1 initial_sigs orig_pairs where - bndrs = map fst pairs - initial_sigs = extendSigEnvList sigs [(id, (initial_sig id, top_lvl)) | id <- bndrs] + bndrs = map fst orig_pairs + initial_sigs = extendSigEnvList sigs [(id, (initialSig id, top_lvl)) | id <- bndrs] loop :: Int -> SigEnv -- Already contains the current sigs -> [(Id,CoreExpr)] -> (SigEnv, DmdEnv, [(Id,CoreExpr)]) loop n sigs pairs - | all (same_sig sigs sigs') bndrs = (sigs', lazy_fv, pairs') + | found_fixpoint + = (sigs', lazy_fv, pairs') -- Note: use pairs', not pairs. pairs' is the result of -- processing the RHSs with sigs (= sigs'), whereas pairs -- is the result of processing the RHSs with the *previous* -- iteration of sigs. - | n >= 5 = pprTrace "dmdFix" (ppr n <+> (vcat + + | n >= 10 = pprTrace "dmdFix loop" (ppr n <+> (vcat [ text "Sigs:" <+> ppr [(id,lookup sigs id, lookup sigs' id) | (id,_) <- pairs], text "env:" <+> ppr (ufmToList sigs), - text "binds:" <+> ppr pairs])) - (loop (n+1) sigs' pairs') - | otherwise = {- pprTrace "dmdFixLoop" (ppr id_sigs) -} (loop (n+1) sigs' pairs') + text "binds:" <+> pprCoreBinding (Rec pairs)])) + (emptySigEnv, lazy_fv, orig_pairs) -- Safe output + -- The lazy_fv part is really important! orig_pairs has no strictness + -- info, including nothing about free vars. But if we have + -- letrec f = ....y..... in ...f... + -- where 'y' is free in f, we must record that y is mentioned, + -- otherwise y will get recorded as absent altogether + + | otherwise = loop (n+1) sigs' pairs' where + found_fixpoint = all (same_sig sigs sigs') bndrs -- Use the new signature to do the next pair -- The occurrence analyser has arranged them in a good order -- so this can significantly reduce the number of iterations needed @@ -290,36 +395,40 @@ dmdFix top_lvl sigs pairs ((sigs', lazy_fv'), pair') -- ) where - (sigs', lazy_fv1, pair') = downRhs top_lvl sigs (id,rhs) + (sigs', lazy_fv1, pair') = dmdAnalRhs top_lvl Recursive sigs (id,rhs) lazy_fv' = plusUFM_C both lazy_fv lazy_fv1 - old_sig = lookup sigs id - new_sig = lookup sigs' id + -- old_sig = lookup sigs id + -- new_sig = lookup sigs' id + same_sig sigs sigs' var = lookup sigs var == lookup sigs' var + lookup sigs var = case lookupVarEnv sigs var of + Just (sig,_) -> sig + -- Get an initial strictness signature from the Id -- itself. That way we make use of earlier iterations -- of the fixpoint algorithm. (Cunning plan.) -- Note that the cunning plan extends to the DmdEnv too, -- since it is part of the strictness signature - initial_sig id = idNewStrictness_maybe id `orElse` botSig +initialSig id = idNewStrictness_maybe id `orElse` botSig - same_sig sigs sigs' var = lookup sigs var == lookup sigs' var - lookup sigs var = case lookupVarEnv sigs var of - Just (sig,_) -> sig - -downRhs :: TopLevelFlag +dmdAnalRhs :: TopLevelFlag -> RecFlag -> SigEnv -> (Id, CoreExpr) -> (SigEnv, DmdEnv, (Id, CoreExpr)) -- Process the RHS of the binding, add the strictness signature -- to the Id, and augment the environment with the signature as well. -downRhs top_lvl sigs (id, rhs) +dmdAnalRhs top_lvl rec_flag sigs (id, rhs) = (sigs', lazy_fv, (id', rhs')) where - arity = exprArity rhs -- The idArity may not be up to date - (rhs_ty, rhs') = dmdAnal sigs (vanillaCall arity) rhs - (lazy_fv, sig_ty) = mkSigTy id arity rhs rhs_ty - id' = id `setIdNewStrictness` sig_ty - sigs' = extendSigEnv top_lvl sigs id sig_ty + arity = idArity id -- The idArity should be up to date + -- The simplifier was run just beforehand + (rhs_dmd_ty, rhs') = dmdAnal sigs (vanillaCall arity) rhs + (lazy_fv, sig_ty) = WARN( arity /= dmdTypeDepth rhs_dmd_ty && not (exprIsTrivial rhs), ppr id ) + -- The RHS can be eta-reduced to just a variable, + -- in which case we should not complain. + mkSigTy top_lvl rec_flag id rhs rhs_dmd_ty + id' = id `setIdNewStrictness` sig_ty + sigs' = extendSigEnv top_lvl sigs id sig_ty \end{code} %************************************************************************ @@ -329,12 +438,129 @@ downRhs top_lvl sigs (id, rhs) %************************************************************************ \begin{code} -mkSigTy :: Id -> Arity -> CoreExpr -> DmdType -> (DmdEnv, StrictSig) --- Take a DmdType and turn it into a StrictSig -mkSigTy id arity rhs (DmdType fv dmds res) - = (lazy_fv, mkStrictSig id arity dmd_ty) +mkTopSigTy :: CoreExpr -> DmdType -> StrictSig + -- Take a DmdType and turn it into a StrictSig + -- NB: not used for never-inline things; hence False +mkTopSigTy rhs dmd_ty = snd (mk_sig_ty False False rhs dmd_ty) + +mkSigTy :: TopLevelFlag -> RecFlag -> Id -> CoreExpr -> DmdType -> (DmdEnv, StrictSig) +mkSigTy top_lvl rec_flag id rhs dmd_ty + = mk_sig_ty never_inline thunk_cpr_ok rhs dmd_ty + where + never_inline = isNeverActive (idInlinePragma id) + maybe_id_dmd = idNewDemandInfo_maybe id + -- Is Nothing the first time round + + thunk_cpr_ok + | isTopLevel top_lvl = False -- Top level things don't get + -- their demandInfo set at all + | isRec rec_flag = False -- Ditto recursive things + | Just dmd <- maybe_id_dmd = isStrictDmd dmd + | otherwise = True -- Optimistic, first time round + -- See notes below +\end{code} + +The thunk_cpr_ok stuff [CPR-AND-STRICTNESS] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +If the rhs is a thunk, we usually forget the CPR info, because +it is presumably shared (else it would have been inlined, and +so we'd lose sharing if w/w'd it into a function. + +However, if the strictness analyser has figured out (in a previous +iteration) that it's strict, then we DON'T need to forget the CPR info. +Instead we can retain the CPR info and do the thunk-splitting transform +(see WorkWrap.splitThunk). + +This made a big difference to PrelBase.modInt, which had something like + modInt = \ x -> let r = ... -> I# v in + ...body strict in r... +r's RHS isn't a value yet; but modInt returns r in various branches, so +if r doesn't have the CPR property then neither does modInt +Another case I found in practice (in Complex.magnitude), looks like this: + let k = if ... then I# a else I# b + in ... body strict in k .... +(For this example, it doesn't matter whether k is returned as part of +the overall result; but it does matter that k's RHS has the CPR property.) +Left to itself, the simplifier will make a join point thus: + let $j k = ...body strict in k... + if ... then $j (I# a) else $j (I# b) +With thunk-splitting, we get instead + let $j x = let k = I#x in ...body strict in k... + in if ... then $j a else $j b +This is much better; there's a good chance the I# won't get allocated. + +The difficulty with this is that we need the strictness type to +look at the body... but we now need the body to calculate the demand +on the variable, so we can decide whether its strictness type should +have a CPR in it or not. Simple solution: + a) use strictness info from the previous iteration + b) make sure we do at least 2 iterations, by doing a second + round for top-level non-recs. Top level recs will get at + least 2 iterations except for totally-bottom functions + which aren't very interesting anyway. + +NB: strictly_demanded is never true of a top-level Id, or of a recursive Id. + +The Nothing case in thunk_cpr_ok [CPR-AND-STRICTNESS] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Demand info now has a 'Nothing' state, just like strictness info. +The analysis works from 'dangerous' towards a 'safe' state; so we +start with botSig for 'Nothing' strictness infos, and we start with +"yes, it's demanded" for 'Nothing' in the demand info. The +fixpoint iteration will sort it all out. + +We can't start with 'not-demanded' because then consider + f x = let + t = ... I# x + in + if ... then t else I# y else f x' + +In the first iteration we'd have no demand info for x, so assume +not-demanded; then we'd get TopRes for f's CPR info. Next iteration +we'd see that t was demanded, and so give it the CPR property, but by +now f has TopRes, so it will stay TopRes. Instead, with the Nothing +setting the first time round, we say 'yes t is demanded' the first +time. + +However, this does mean that for non-recursive bindings we must +iterate twice to be sure of not getting over-optimistic CPR info, +in the case where t turns out to be not-demanded. This is handled +by dmdAnalTopBind. + + +\begin{code} +mk_sig_ty never_inline thunk_cpr_ok rhs (DmdType fv dmds res) + | never_inline && not (isBotRes res) + -- HACK ALERT + -- Don't strictness-analyse NOINLINE things. Why not? Because + -- the NOINLINE says "don't expose any of the inner workings at the call + -- site" and the strictness is certainly an inner working. + -- + -- More concretely, the demand analyser discovers the following strictness + -- for unsafePerformIO: C(U(AV)) + -- But then consider + -- unsafePerformIO (\s -> let r = f x in + -- case writeIORef v r s of (# s1, _ #) -> + -- (# s1, r #) + -- The strictness analyser will find that the binding for r is strict, + -- (becuase of uPIO's strictness sig), and so it'll evaluate it before + -- doing the writeIORef. This actually makes tests/lib/should_run/memo002 + -- get a deadlock! + -- + -- Solution: don't expose the strictness of unsafePerformIO. + -- + -- But we do want to expose the strictness of error functions, + -- which are also often marked NOINLINE + -- {-# NOINLINE foo #-} + -- foo x = error ("wubble buggle" ++ x) + -- So (hack, hack) we only drop the strictness for non-bottom things + -- This is all very unsatisfactory. + = (deferEnv fv, topSig) + + | otherwise + = (lazy_fv, mkStrictSig dmd_ty) where - dmd_ty = DmdType strict_fv lazified_dmds res' + dmd_ty = DmdType strict_fv final_dmds res' lazy_fv = filterUFM (not . isStrictDmd) fv strict_fv = filterUFM isStrictDmd fv @@ -368,28 +594,13 @@ mkSigTy id arity rhs (DmdType fv dmds res) -- DmdType, because that makes fixpointing very slow --- the -- DmdType gets full of lazy demands that are slow to converge. - lazified_dmds = map lazify dmds - -- Get rid of defers in the arguments - final_dmds = setUnpackStrategy lazified_dmds + final_dmds = setUnpackStrategy dmds -- Set the unpacking strategy - res' = case (dmds, res) of - ([], RetCPR) | not (exprIsValue rhs) -> TopRes - other -> res - -- If the rhs is a thunk, we forget the CPR info, because - -- it is presumably shared (else it would have been inlined, and - -- so we'd lose sharing if w/w'd it into a function. - -- - -- DONE IN OLD CPR ANALYSER, BUT NOT YET HERE - -- Also, if the strictness analyser has figured out that it's strict, - -- the let-to-case transformation will happen, so again it's good. - -- (CPR analysis runs before the simplifier has had a chance to do - -- the let-to-case transform.) - -- This made a big difference to PrelBase.modInt, which had something like - -- modInt = \ x -> let r = ... -> I# v in - -- ...body strict in r... - -- r's RHS isn't a value yet; but modInt returns r in various branches, so - -- if r doesn't have the CPR property then neither does modInt + res' = case res of + RetCPR | ignore_cpr_info -> TopRes + other -> res + ignore_cpr_info = not (exprIsHNF rhs || thunk_cpr_ok) \end{code} The unpack strategy determines whether we'll *really* unpack the argument, @@ -405,15 +616,13 @@ setUnpackStrategy ds -> [Demand] -> (Int, [Demand]) -- Args remaining after subcomponents of [Demand] are unpacked - go n (Seq keep _ cs : ds) - | n' >= 0 = Seq keep Now cs' `cons` go n'' ds - | otherwise = Eval `cons` go n ds + go n (Eval (Prod cs) : ds) + | n' >= 0 = Eval (Prod cs') `cons` go n'' ds + | otherwise = Box (Eval (Prod cs)) `cons` go n ds where (n'',cs') = go n' cs - n' = n + box - non_abs_args - box = case keep of - Keep -> 0 - Drop -> 1 -- Add one to the budget if we drop the top-level arg + n' = n + 1 - non_abs_args + -- Add one to the budget 'cos we drop the top-level arg non_abs_args = nonAbsentArgs cs -- Delete # of non-absent args to which we'll now be committed @@ -438,12 +647,10 @@ nonAbsentArgs (d : ds) = 1 + nonAbsentArgs ds \begin{code} splitDmdTy :: DmdType -> (Demand, DmdType) -- Split off one function argument +-- We already have a suitable demand on all +-- free vars, so no need to add more! splitDmdTy (DmdType fv (dmd:dmds) res_ty) = (dmd, DmdType fv dmds res_ty) -splitDmdTy ty@(DmdType fv [] TopRes) = (topDmd, ty) -splitDmdTy ty@(DmdType fv [] BotRes) = (Abs, ty) - -- We already have a suitable demand on all - -- free vars, so no need to add more! -splitDmdTy (DmdType fv [] RetCPR) = panic "splitDmdTy" +splitDmdTy ty@(DmdType fv [] res_ty) = (resTypeArgDmd res_ty, ty) \end{code} \begin{code} @@ -454,7 +661,35 @@ addVarDmd top_lvl dmd_ty@(DmdType fv ds res) var dmd | otherwise = DmdType (extendVarEnv fv var dmd) ds res addLazyFVs (DmdType fv ds res) lazy_fvs - = DmdType (plusUFM_C both fv lazy_fvs) ds res + = DmdType both_fv1 ds res + where + both_fv = (plusUFM_C both fv lazy_fvs) + both_fv1 = modifyEnv (isBotRes res) (`both` Bot) lazy_fvs fv both_fv + -- This modifyEnv is vital. Consider + -- let f = \x -> (x,y) + -- in error (f 3) + -- Here, y is treated as a lazy-fv of f, but we must `both` that L + -- demand with the bottom coming up from 'error' + -- + -- I got a loop in the fixpointer without this, due to an interaction + -- with the lazy_fv filtering in mkSigTy. Roughly, it was + -- letrec f n x + -- = letrec g y = x `fatbar` + -- letrec h z = z + ...g... + -- in h (f (n-1) x) + -- in ... + -- In the initial iteration for f, f=Bot + -- Suppose h is found to be strict in z, but the occurrence of g in its RHS + -- is lazy. Now consider the fixpoint iteration for g, esp the demands it + -- places on its free variables. Suppose it places none. Then the + -- x `fatbar` ...call to h... + -- will give a x->V demand for x. That turns into a L demand for x, + -- which floats out of the defn for h. Without the modifyEnv, that + -- L demand doesn't get both'd with the Bot coming up from the inner + -- call to f. So we just get an L demand for x for g. + -- + -- A better way to say this is that the lazy-fv filtering should give the + -- same answer as putting the lazy fv demands in the function's type. annotateBndr :: DmdType -> Var -> (DmdType, Var) -- The returned env has the var deleted @@ -472,16 +707,31 @@ annotateLamIdBndr dmd_ty@(DmdType fv ds res) id -- For lambdas we add the demand to the argument demands -- Only called for Ids = ASSERT( isId id ) - (DmdType fv' (dmd:ds) res, setIdNewDemandInfo id dmd) + (DmdType fv' (hacked_dmd:ds) res, setIdNewDemandInfo id hacked_dmd) where (fv', dmd) = removeFV fv id res - -removeFV fv var res = (fv', dmd) + hacked_dmd = argDemand dmd + -- This call to argDemand is vital, because otherwise we label + -- a lambda binder with demand 'B'. But in terms of calling + -- conventions that's Abs, because we don't pass it. But + -- when we do a w/w split we get + -- fw x = (\x y:B -> ...) x (error "oops") + -- And then the simplifier things the 'B' is a strict demand + -- and evaluates the (error "oops"). Sigh + +removeFV fv id res = (fv', zapUnlifted id dmd) where - fv' = fv `delVarEnv` var - dmd = lookupVarEnv fv var `orElse` deflt + fv' = fv `delVarEnv` id + dmd = lookupVarEnv fv id `orElse` deflt deflt | isBotRes res = Bot | otherwise = Abs + +-- For unlifted-type variables, we are only +-- interested in Bot/Abs/Box Abs +zapUnlifted is Bot = Bot +zapUnlifted id Abs = Abs +zapUnlifted id dmd | isUnLiftedType (idType id) = lazyDmd + | otherwise = dmd \end{code} %************************************************************************ @@ -506,6 +756,31 @@ extendSigEnv top_lvl env var sig = extendVarEnv env var (sig, top_lvl) extendSigEnvList = extendVarEnvList +extendSigsWithLam :: SigEnv -> Id -> SigEnv +-- Extend the SigEnv when we meet a lambda binder +-- If the binder is marked demanded with a product demand, then give it a CPR +-- signature, because in the likely event that this is a lambda on a fn defn +-- [we only use this when the lambda is being consumed with a call demand], +-- it'll be w/w'd and so it will be CPR-ish. E.g. +-- f = \x::(Int,Int). if ...strict in x... then +-- x +-- else +-- (a,b) +-- We want f to have the CPR property because x does, by the time f has been w/w'd +-- +-- Also note that we only want to do this for something that +-- definitely has product type, else we may get over-optimistic +-- CPR results (e.g. from \x -> x!). + +extendSigsWithLam sigs id + = case idNewDemandInfo_maybe id of + Nothing -> extendVarEnv sigs id (cprSig, NotTopLevel) + -- Optimistic in the Nothing case; + -- See notes [CPR-AND-STRICTNESS] + Just (Eval (Prod ds)) -> extendVarEnv sigs id (cprSig, NotTopLevel) + other -> sigs + + dmdTransform :: SigEnv -- The strictness environment -> Id -- The function -> Demand -- The demand on the function @@ -516,19 +791,40 @@ dmdTransform :: SigEnv -- The strictness environment dmdTransform sigs var dmd ------ DATA CONSTRUCTOR - | isDataConId var, -- Data constructor - Seq k Now ds <- res_dmd, -- and the demand looks inside its fields - let StrictSig dmd_ty = idNewStrictness var -- It must have a strictness sig - = if dmdTypeDepth dmd_ty == length ds then -- Saturated, so unleash the demand - -- ds can be empty, when we are just seq'ing the thing - mkDmdType emptyDmdEnv ds (dmdTypeRes dmd_ty) - -- Need to extract whether it's a product, hence dmdTypeRes + | isDataConWorkId var -- Data constructor + = let + StrictSig dmd_ty = idNewStrictness var -- It must have a strictness sig + DmdType _ _ con_res = dmd_ty + arity = idArity var + in + if arity == call_depth then -- Saturated, so unleash the demand + let + -- Important! If we Keep the constructor application, then + -- we need the demands the constructor places (always lazy) + -- If not, we don't need to. For example: + -- f p@(x,y) = (p,y) -- S(AL) + -- g a b = f (a,b) + -- It's vital that we don't calculate Absent for a! + dmd_ds = case res_dmd of + Box (Eval ds) -> mapDmds box ds + Eval ds -> ds + other -> Poly Top + + -- ds can be empty, when we are just seq'ing the thing + -- If so we must make up a suitable bunch of demands + arg_ds = case dmd_ds of + Poly d -> replicate arity d + Prod ds -> ASSERT( ds `lengthIs` arity ) ds + + in + mkDmdType emptyDmdEnv arg_ds con_res + -- Must remember whether it's a product, hence con_res, not TopRes else topDmdType ------ IMPORTED FUNCTION | isGlobalId var, -- Imported function - let StrictSig dmd_ty = getNewStrictness var + let StrictSig dmd_ty = idNewStrictness var = if dmdTypeDepth dmd_ty <= call_depth then -- Saturated, so unleash the demand dmd_ty else @@ -568,171 +864,61 @@ splitCallDmd (Call d) = case splitCallDmd d of splitCallDmd d = (0, d) vanillaCall :: Arity -> Demand -vanillaCall 0 = Eval +vanillaCall 0 = evalDmd vanillaCall n = Call (vanillaCall (n-1)) deferType :: DmdType -> DmdType -deferType (DmdType fv _ _) = DmdType (mapVarEnv defer fv) [] TopRes +deferType (DmdType fv _ _) = DmdType (deferEnv fv) [] TopRes -- Notice that we throw away info about both arguments and results -- For example, f = let ... in \x -> x -- We don't want to get a stricness type V->T for f. + -- Peter?? -defer :: Demand -> Demand --- c.f. `lub` Abs -defer Abs = Abs -defer (Seq k _ ds) = Seq k Defer ds -defer other = Lazy +deferEnv :: DmdEnv -> DmdEnv +deferEnv fv = mapVarEnv defer fv -lazify :: Demand -> Demand --- The 'Defer' demands are just Lazy at function boundaries -lazify (Seq k Defer ds) = Lazy -lazify (Seq k Now ds) = Seq k Now (map lazify ds) -lazify Bot = Abs -- Don't pass args that are consumed by bottom -lazify d = d -\end{code} -\begin{code} -betterStrictness :: StrictSig -> StrictSig -> Bool -betterStrictness (StrictSig t1) (StrictSig t2) = betterDmdType t1 t2 - -betterDmdType t1 t2 = (t1 `lubType` t2) == t2 - -betterDemand :: Demand -> Demand -> Bool --- If d1 `better` d2, and d2 `better` d2, then d1==d2 -betterDemand d1 d2 = (d1 `lub` d2) == d2 - -squashDmdEnv (StrictSig (DmdType fv ds res)) = StrictSig (DmdType emptyDmdEnv ds res) +---------------- +argDemand :: Demand -> Demand +-- The 'Defer' demands are just Lazy at function boundaries +-- Ugly! Ask John how to improve it. +argDemand Top = lazyDmd +argDemand (Defer d) = lazyDmd +argDemand (Eval ds) = Eval (mapDmds argDemand ds) +argDemand (Box Bot) = evalDmd +argDemand (Box d) = box (argDemand d) +argDemand Bot = Abs -- Don't pass args that are consumed (only) by bottom +argDemand d = d \end{code} - -%************************************************************************ -%* * -\subsection{LUB and BOTH} -%* * -%************************************************************************ - \begin{code} -lub :: Demand -> Demand -> Demand - -lub Bot d = d - -lub Lazy d = Lazy - -lub Err Bot = Err -lub Err d = d - -lub Abs Bot = Abs -lub Abs Err = Abs -lub Abs Abs = Abs -lub Abs (Seq k _ ds) = Seq k Defer ds -- Very important ('radicals' example) -lub Abs d = Lazy - -lub Eval Abs = Lazy -lub Eval Lazy = Lazy -lub Eval (Seq k Now ds) = Seq Keep Now ds -lub Eval d = Eval - -lub (Call d1) (Call d2) = Call (lub d1 d2) - -lub (Seq k1 l1 ds1) (Seq k2 l2 ds2) = Seq (k1 `vee` k2) (l1 `or_defer` l2) (lubs ds1 ds2) - --- The last clauses deal with the remaining cases for Call and Seq -lub d1@(Call _) d2@(Seq _ _ _) = pprPanic "lub" (ppr d1 $$ ppr d2) -lub d1 d2 = lub d2 d1 - --- A Seq can have an empty list of demands, in the polymorphic case. -lubs [] ds2 = ds2 -lubs ds1 [] = ds1 -lubs ds1 ds2 = ASSERT( length ds1 == length ds2 ) zipWith lub ds1 ds2 - -or_defer Now Now = Now -or_defer _ _ = Defer - ------------------------- -- Consider (if x then y else []) with demand V -- Then the first branch gives {y->V} and the second --- *implicitly* has {y->A}. So we must put {y->(V `lub` A)} +-- *implicitly* has {y->A}. So we must put {y->(V `lub` A)} -- in the result env. lubType (DmdType fv1 ds1 r1) (DmdType fv2 ds2 r2) - = DmdType lub_fv2 (zipWith lub ds1 ds2) (r1 `lubRes` r2) + = DmdType lub_fv2 (lub_ds ds1 ds2) (r1 `lubRes` r2) where lub_fv = plusUFM_C lub fv1 fv2 - lub_fv1 = modifyEnv (not (isBotRes r1)) (Abs `lub`) fv2 fv1 lub_fv - lub_fv2 = modifyEnv (not (isBotRes r2)) (Abs `lub`) fv1 fv2 lub_fv1 + lub_fv1 = modifyEnv (not (isBotRes r1)) absLub fv2 fv1 lub_fv + lub_fv2 = modifyEnv (not (isBotRes r2)) absLub fv1 fv2 lub_fv1 -- lub is the identity for Bot -------------------------- -lubRes BotRes r = r -lubRes r BotRes = r -lubRes RetCPR RetCPR = RetCPR -lubRes r1 r2 = TopRes - ------------------------------------ -vee :: Keepity -> Keepity -> Keepity -vee Drop Drop = Drop -vee k1 k2 = Keep - ------------------------------------ -both :: Demand -> Demand -> Demand - --- The normal one --- both Bot d = Bot - --- The experimental one --- The idea is that (error x) places on x --- both demand Bot (like on all free vars) --- and demand Eval (for the arg to error) --- and we want the result to be Eval. -both Bot Bot = Bot -both Bot Abs = Bot -both Bot d = d - -both Abs d = d - -both Err Bot = Err -both Err Abs = Err -both Err d = d - -both Lazy Bot = Lazy -both Lazy Abs = Lazy -both Lazy Err = Lazy -both Lazy (Seq k Now ds) = Seq Keep Now ds -both Lazy d = d - -both Eval (Seq k l ds) = Seq Keep Now ds -both Eval (Call d) = Call d -both Eval d = Eval - -both (Seq k1 Defer ds1) (Seq k2 Defer ds2) = Seq (k1 `vee` k2) Defer (boths ds1 ds2) -both (Seq k1 l1 ds1) (Seq k2 l2 ds2) = Seq (k1 `vee` k2) Now (boths ds1' ds2') - where - ds1' = case l1 of { Now -> ds1; Defer -> map defer ds1 } - ds2' = case l2 of { Now -> ds2; Defer -> map defer ds2 } - -both (Call d1) (Call d2) = Call (d1 `both` d2) - --- The last clauses deal with the remaining cases for Call and Seq -both d1@(Call _) d2@(Seq _ _ _) = pprPanic "both" (ppr d1 $$ ppr d2) -both d1 d2 = both d2 d1 - ------------------------------------ --- A Seq can have an empty list of demands, in the polymorphic case. -boths [] ds2 = ds2 -boths ds1 [] = ds1 -boths ds1 ds2 = ASSERT( length ds1 == length ds2 ) zipWith both ds1 ds2 - ------------------------------------ -bothRes :: DmdResult -> DmdResult -> DmdResult --- Left-biased for CPR info -bothRes BotRes _ = BotRes -bothRes _ BotRes = BotRes -bothRes r1 _ = r1 + -- Extend the shorter argument list to match the longer + lub_ds (d1:ds1) (d2:ds2) = lub d1 d2 : lub_ds ds1 ds2 + lub_ds [] [] = [] + lub_ds ds1 [] = map (`lub` resTypeArgDmd r2) ds1 + lub_ds [] ds2 = map (resTypeArgDmd r1 `lub`) ds2 ----------------------------------- -- (t1 `bothType` t2) takes the argument/result info from t1, -- using t2 just for its free-var info +-- NB: Don't forget about r2! It might be BotRes, which is +-- a bottom demand on all the in-scope variables. +-- Peter: can this be done more neatly? bothType (DmdType fv1 ds1 r1) (DmdType fv2 ds2 r2) - = DmdType both_fv2 ds1 r1 + = DmdType both_fv2 ds1 (r1 `bothRes` r2) where both_fv = plusUFM_C both fv1 fv2 both_fv1 = modifyEnv (isBotRes r1) (`both` Bot) fv2 fv1 both_fv @@ -740,6 +926,19 @@ bothType (DmdType fv1 ds1 r1) (DmdType fv2 ds2 r2) -- both is the identity for Abs \end{code} + +\begin{code} +lubRes BotRes r = r +lubRes r BotRes = r +lubRes RetCPR RetCPR = RetCPR +lubRes r1 r2 = TopRes + +-- If either diverges, the whole thing does +-- Otherwise take CPR info from the first +bothRes r1 BotRes = BotRes +bothRes r1 r2 = r1 +\end{code} + \begin{code} modifyEnv :: Bool -- No-op if False -> (Demand -> Demand) -- The zapper @@ -760,20 +959,164 @@ modifyEnv need_to_modify zapper env1 env2 env %************************************************************************ %* * +\subsection{LUB and BOTH} +%* * +%************************************************************************ + +\begin{code} +lub :: Demand -> Demand -> Demand + +lub Bot d2 = d2 +lub Abs d2 = absLub d2 +lub Top d2 = Top +lub (Defer ds1) d2 = defer (Eval ds1 `lub` d2) + +lub (Call d1) (Call d2) = Call (d1 `lub` d2) +lub d1@(Call _) (Box d2) = d1 `lub` d2 -- Just strip the box +lub d1@(Call _) d2@(Eval _) = d2 -- Presumably seq or vanilla eval +lub d1@(Call _) d2 = d2 `lub` d1 -- Bot, Abs, Top + +-- For the Eval case, we use these approximation rules +-- Box Bot <= Eval (Box Bot ...) +-- Box Top <= Defer (Box Bot ...) +-- Box (Eval ds) <= Eval (map Box ds) +lub (Eval ds1) (Eval ds2) = Eval (ds1 `lubs` ds2) +lub (Eval ds1) (Box Bot) = Eval (mapDmds (`lub` Box Bot) ds1) +lub (Eval ds1) (Box (Eval ds2)) = Eval (ds1 `lubs` mapDmds box ds2) +lub (Eval ds1) (Box Abs) = deferEval (mapDmds (`lub` Box Bot) ds1) +lub d1@(Eval _) d2 = d2 `lub` d1 -- Bot,Abs,Top,Call,Defer + +lub (Box d1) (Box d2) = box (d1 `lub` d2) +lub d1@(Box _) d2 = d2 `lub` d1 + +lubs = zipWithDmds lub + +--------------------- +-- box is the smart constructor for Box +-- It computes & d +-- INVARIANT: (Box d) => d = Bot, Abs, Eval +-- Seems to be no point in allowing (Box (Call d)) +box (Call d) = Call d -- The odd man out. Why? +box (Box d) = Box d +box (Defer _) = lazyDmd +box Top = lazyDmd -- Box Abs and Box Top +box Abs = lazyDmd -- are the same +box d = Box d -- Bot, Eval + +--------------- +defer :: Demand -> Demand + +-- defer is the smart constructor for Defer +-- The idea is that (Defer ds) = +-- +-- It specifies what happens at a lazy function argument +-- or a lambda; the L* operator +-- Set the strictness part to L, but leave +-- the boxity side unaffected +-- It also ensures that Defer (Eval [LLLL]) = L + +defer Bot = Abs +defer Abs = Abs +defer Top = Top +defer (Call _) = lazyDmd -- Approximation here? +defer (Box _) = lazyDmd +defer (Defer ds) = Defer ds +defer (Eval ds) = deferEval ds + +-- deferEval ds = defer (Eval ds) +deferEval ds | allTop ds = Top + | otherwise = Defer ds + +--------------------- +absLub :: Demand -> Demand +-- Computes (Abs `lub` d) +-- For the Bot case consider +-- f x y = if ... then x else error x +-- Then for y we get Abs `lub` Bot, and we really +-- want Abs overall +absLub Bot = Abs +absLub Abs = Abs +absLub Top = Top +absLub (Call _) = Top +absLub (Box _) = Top +absLub (Eval ds) = Defer (absLubs ds) -- Or (Defer ds)? +absLub (Defer ds) = Defer (absLubs ds) -- Or (Defer ds)? + +absLubs = mapDmds absLub + +--------------- +both :: Demand -> Demand -> Demand + +both Abs d2 = d2 + +both Bot Bot = Bot +both Bot Abs = Bot +both Bot (Eval ds) = Eval (mapDmds (`both` Bot) ds) + -- Consider + -- f x = error x + -- From 'error' itself we get demand Bot on x + -- From the arg demand on x we get + -- x :-> evalDmd = Box (Eval (Poly Abs)) + -- So we get Bot `both` Box (Eval (Poly Abs)) + -- = Seq Keep (Poly Bot) + -- + -- Consider also + -- f x = if ... then error (fst x) else fst x + -- Then we get (Eval (Box Bot, Bot) `lub` Eval (SA)) + -- = Eval (SA) + -- which is what we want. +both Bot d = errDmd + +both Top Bot = errDmd +both Top Abs = Top +both Top Top = Top +both Top (Box d) = Box d +both Top (Call d) = Call d +both Top (Eval ds) = Eval (mapDmds (`both` Top) ds) +both Top (Defer ds) -- = defer (Top `both` Eval ds) + -- = defer (Eval (mapDmds (`both` Top) ds)) + = deferEval (mapDmds (`both` Top) ds) + + +both (Box d1) (Box d2) = box (d1 `both` d2) +both (Box d1) d2@(Call _) = box (d1 `both` d2) +both (Box d1) d2@(Eval _) = box (d1 `both` d2) +both (Box d1) (Defer d2) = Box d1 +both d1@(Box _) d2 = d2 `both` d1 + +both (Call d1) (Call d2) = Call (d1 `both` d2) +both (Call d1) (Eval ds2) = Call d1 -- Could do better for (Poly Bot)? +both (Call d1) (Defer ds2) = Call d1 -- Ditto +both d1@(Call _) d2 = d1 `both` d1 + +both (Eval ds1) (Eval ds2) = Eval (ds1 `boths` ds2) +both (Eval ds1) (Defer ds2) = Eval (ds1 `boths` mapDmds defer ds2) +both d1@(Eval ds1) d2 = d2 `both` d1 + +both (Defer ds1) (Defer ds2) = deferEval (ds1 `boths` ds2) +both d1@(Defer ds1) d2 = d2 `both` d1 + +boths = zipWithDmds both +\end{code} + + + +%************************************************************************ +%* * \subsection{Miscellaneous %* * %************************************************************************ \begin{code} +#ifdef OLD_STRICTNESS get_changes binds = vcat (map get_changes_bind binds) get_changes_bind (Rec pairs) = vcat (map get_changes_pr pairs) get_changes_bind (NonRec id rhs) = get_changes_pr (id,rhs) get_changes_pr (id,rhs) - | isImplicitId id = empty -- We don't look inside these - | otherwise = get_changes_var id $$ get_changes_expr rhs + = get_changes_var id $$ get_changes_expr rhs get_changes_var var | isId var = get_changes_str var $$ get_changes_dmd var @@ -798,8 +1141,9 @@ get_changes_str id where message word = text word <+> text "strictness for" <+> ppr id <+> info info = (text "Old" <+> ppr old) $$ (text "New" <+> ppr new) - new = squashDmdEnv (idNewStrictness id) -- Don't report diffs in the env - old = newStrictnessFromOld id + new = squashSig (idNewStrictness id) -- Don't report spurious diffs that the old + -- strictness analyser can't track + old = newStrictnessFromOld (idName id) (idArity id) (idStrictness id) (idCprInfo id) old_better = old `betterStrictness` new new_better = new `betterStrictness` old @@ -812,8 +1156,30 @@ get_changes_dmd id where message word = text word <+> text "demand for" <+> ppr id <+> info info = (text "Old" <+> ppr old) $$ (text "New" <+> ppr new) - new = lazify (idNewDemandInfo id) -- Lazify to avoid spurious improvements + new = squashDmd (argDemand (idNewDemandInfo id)) -- To avoid spurious improvements + -- A bit of a hack old = newDemand (idDemandInfo id) new_better = new `betterDemand` old old_better = old `betterDemand` new + +betterStrictness :: StrictSig -> StrictSig -> Bool +betterStrictness (StrictSig t1) (StrictSig t2) = betterDmdType t1 t2 + +betterDmdType t1 t2 = (t1 `lubType` t2) == t2 + +betterDemand :: Demand -> Demand -> Bool +-- If d1 `better` d2, and d2 `better` d2, then d1==d2 +betterDemand d1 d2 = (d1 `lub` d2) == d2 + +squashSig (StrictSig (DmdType fv ds res)) + = StrictSig (DmdType emptyDmdEnv (map squashDmd ds) res) + where + -- squash just gets rid of call demands + -- which the old analyser doesn't track +squashDmd (Call d) = evalDmd +squashDmd (Box d) = Box (squashDmd d) +squashDmd (Eval ds) = Eval (mapDmds squashDmd ds) +squashDmd (Defer ds) = Defer (mapDmds squashDmd ds) +squashDmd d = d +#endif \end{code}