#include "HsVersions.h"
-import CmdLineOpts ( DynFlags, DynFlag(..) )
+import CmdLineOpts ( DynFlags, DynFlag(..), opt_MaxWorkerArgs )
import NewDemand -- All of it
import CoreSyn
+import CoreUtils ( exprIsValue, exprArity )
import DataCon ( dataConTyCon )
import TyCon ( isProductTyCon, isRecursiveTyCon )
-import Id ( Id, idInfo, idArity, idStrictness, idCprInfo, idDemandInfo,
- modifyIdInfo, isDataConId, isImplicitId )
-import IdInfo ( newStrictnessInfo, setNewStrictnessInfo, mkNewStrictnessInfo,
- newDemandInfo, setNewDemandInfo, newDemand
- )
+import Id ( Id, idType, idInfo, idArity, idCprInfo, idDemandInfo,
+ modifyIdInfo, isDataConId, isImplicitId, isGlobalId,
+ idNewStrictness, idNewStrictness_maybe, getNewStrictness, setIdNewStrictness,
+ idNewDemandInfo, setIdNewDemandInfo, newStrictnessFromOld )
+import IdInfo ( newDemand )
import Var ( Var )
import VarEnv
-import UniqFM ( plusUFM_C, addToUFM_Directly, keysUFM, minusUFM )
+import UniqFM ( plusUFM_C, addToUFM_Directly, lookupUFM_Directly,
+ keysUFM, minusUFM, ufmToList, filterUFM )
+import Type ( isUnLiftedType )
import CoreLint ( showPass, endPass )
import ErrUtils ( dumpIfSet_dyn )
-import Util ( mapAccumL, mapAccumR, zipWithEqual )
-import BasicTypes ( Arity )
-import Maybes ( orElse )
+import Util ( mapAndUnzip, mapAccumL, mapAccumR, zipWithEqual )
+import BasicTypes ( Arity, TopLevelFlag(..), isTopLevel )
+import Maybes ( orElse, expectJust )
import Outputable
import FastTypes
\end{code}
-ToDo: set a noinline pragma on bottoming Ids
+To think about
+
+* set a noinline pragma on bottoming Ids
+
+* 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}
%************************************************************************
%* *
\begin{code}
dmdAnalPgm :: DynFlags -> [CoreBind] -> IO [CoreBind]
-#ifndef DEBUG
-
-dmdAnalPgm dflags binds = return binds
-
-#else
-
+dmdAnalPgm dflags binds
+ = panic "dmdAnalPgm called"
dmdAnalPgm dflags binds
= do {
showPass dflags "Demand analysis" ;
dmd_changes = get_changes binds_plus_dmds } ;
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
printDump (text "Changes in demands" $$ dmd_changes) ;
+#endif
return binds_plus_dmds
}
where
= (sigs, NonRec id rhs) -- It's pre-computed in MkId.lhs
| otherwise
= let
- (sig, rhs_env, (id', rhs')) = downRhs sigs (id, rhs)
- sigs' = extendSigEnv sigs id sig
+ (sigs', _, (id', rhs')) = downRhs TopLevel sigs (id, rhs)
in
(sigs', NonRec id' rhs')
dmdAnalTopBind sigs (Rec pairs)
= let
- (sigs', _, pairs') = dmdFix sigs pairs
+ (sigs', _, pairs') = dmdFix TopLevel sigs pairs
in
(sigs', Rec pairs')
\end{code}
%************************************************************************
\begin{code}
-dmdAnal :: SigEnv -> Demand -> CoreExpr -> (DmdType, DmdEnv, CoreExpr)
+dmdAnal :: SigEnv -> Demand -> CoreExpr -> (DmdType, CoreExpr)
-dmdAnal sigs Abs e = (DmdRes TopRes, emptyDmdEnv, e)
+dmdAnal sigs Abs e = (topDmdType, e)
dmdAnal sigs Lazy e = let
- (res_ty, dmd_env, e') = dmdAnal sigs Eval e
+ (res_ty, e') = dmdAnal sigs Eval e
in
- (res_ty, lazify dmd_env, e')
+ (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
- -- that is wrong, and we'd need to reduce the demand on s (inconvenient)
+ -- that is wrong, and we'd need to reduce the demand on s,
+ -- which is inconvenient
-- b) More important, consider
-- f (let x = R in x+x), where f is lazy
-- We still want to mark x as demanded, because it will be when we
-- just mark x as Lazy
-dmdAnal sigs dmd (Var var)
- = (res_ty,
- blackHoleEnv res_ty (unitDmdEnv var dmd),
- Var var)
- where
- res_ty = dmdTransform sigs var dmd
-
dmdAnal sigs dmd (Lit lit)
- = (topDmdType, emptyDmdEnv, Lit lit)
+ = (topDmdType, Lit lit)
+
+dmdAnal sigs dmd (Var var)
+ = (dmdTransform sigs var dmd, Var var)
dmdAnal sigs dmd (Note n e)
- = (dmd_ty, dmd_env, Note n e')
+ = (dmd_ty, Note n e')
where
- (dmd_ty, dmd_env, e') = dmdAnal sigs dmd e
+ (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
dmdAnal sigs dmd (App fun (Type ty))
- = (fun_ty, fun_env, App fun' (Type ty))
+ = (fun_ty, App fun' (Type ty))
where
- (fun_ty, fun_env, fun') = dmdAnal sigs dmd fun
+ (fun_ty, fun') = dmdAnal sigs dmd fun
dmdAnal sigs dmd (App fun arg) -- Non-type arguments
= let -- [Type arg handled above]
- (fun_ty, fun_env, fun') = dmdAnal sigs (Call dmd) fun
- (arg_ty, arg_env, arg') = dmdAnal sigs arg_dmd arg
- (arg_dmd, res_ty) = splitDmdTy fun_ty
+ (fun_ty, fun') = dmdAnal sigs (Call dmd) fun
+ (arg_ty, arg') = dmdAnal sigs arg_dmd arg
+ (arg_dmd, res_ty) = splitDmdTy fun_ty
in
- (res_ty,
- blackHoleEnv res_ty (fun_env `bothEnv` arg_env),
- App fun' arg')
+ (res_ty `bothType` arg_ty, App fun' arg')
dmdAnal sigs dmd (Lam var body)
| isTyVar var
= let
- (body_ty, body_env, body') = dmdAnal sigs dmd body
+ (body_ty, body') = dmdAnal sigs dmd body
in
- (body_ty, body_env, Lam var body')
+ (body_ty, Lam var body')
- | otherwise
- = let
- body_dmd = case dmd of
- Call dmd -> dmd
- other -> Lazy -- Conservative
+ | Call body_dmd <- dmd -- A call demand: good!
+ = let
+ (body_ty, body') = dmdAnal sigs body_dmd body
+ (lam_ty, var') = annotateLamIdBndr body_ty var
+ in
+ (lam_ty, Lam var' body')
- (body_ty, body_env, body') = dmdAnal sigs body_dmd body
- (lam_env, var') = annotateBndr body_env var
+ | 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
+ (lam_ty, var') = annotateLamIdBndr body_ty var
in
- (DmdFun (idNewDemandInfo var') body_ty,
- body_env `delDmdEnv` var,
- Lam var' body')
+ (deferType lam_ty, Lam var' body')
dmdAnal sigs dmd (Case scrut case_bndr [alt@(DataAlt dc,bndrs,rhs)])
| let tycon = dataConTyCon dc,
isProductTyCon tycon,
not (isRecursiveTyCon tycon)
= let
- bndr_ids = filter isId bndrs
- (alt_ty, alt_env, alt') = dmdAnalAlt sigs dmd alt
- (_, scrut_env, scrut') = dmdAnal sigs scrut_dmd scrut
- (alt_env2, case_bndr') = annotateBndr alt_env case_bndr
- (_, bndrs', _) = alt'
- scrut_dmd = Seq Drop [idNewDemandInfo b | b <- bndrs', isId b]
+ 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.
+ -- 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
in
- (alt_ty,
- alt_env2 `bothEnv` scrut_env,
- Case scrut' case_bndr' [alt'])
+ (alt_ty1 `bothType` scrut_ty, Case scrut' case_bndr' [alt'])
dmdAnal sigs dmd (Case scrut case_bndr alts)
= let
- (alt_tys, alt_envs, alts') = unzip3 (map (dmdAnalAlt sigs dmd) alts)
- (scrut_ty, scrut_env, scrut') = dmdAnal sigs Eval scrut
- (alt_env2, case_bndr') = annotateBndr (foldr1 lubEnv alt_envs) case_bndr
+ (alt_tys, alts') = mapAndUnzip (dmdAnalAlt sigs dmd) alts
+ (scrut_ty, scrut') = dmdAnal sigs Eval scrut
+ (alt_ty, case_bndr') = annotateBndr (foldr1 lubType alt_tys) case_bndr
in
- (foldr1 lubDmdTy alt_tys,
- alt_env2 `bothEnv` scrut_env,
- Case scrut' case_bndr' alts')
+-- pprTrace "dmdAnal:Case" (ppr alts $$ ppr alt_tys)
+ (alt_ty `bothType` scrut_ty, Case scrut' case_bndr' alts')
dmdAnal sigs dmd (Let (NonRec id rhs) body)
- | idArity id == 0 -- A thunk; analyse the body first, then the thunk
= let
- (body_ty, body_env, body') = dmdAnal sigs dmd body
- (rhs_ty, rhs_env, rhs') = dmdAnal sigs (lookupDmd body_env id) rhs
- (body_env1, id1) = annotateBndr body_env id
+ (sigs', lazy_fv, (id1, rhs')) = downRhs NotTopLevel 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
- (body_ty, body_env1 `bothEnv` rhs_env, Let (NonRec id1 rhs') body')
-
- | otherwise -- A function; analyse the function first, then the body
- = let
- (sig, rhs_env, (id1, rhs')) = downRhs sigs (id, rhs)
- sigs' = extendSigEnv sigs id sig
- (body_ty, body_env, body') = dmdAnal sigs' dmd body
- rhs_env1 = weaken body_env id rhs_env
- (body_env1, id2) = annotateBndr body_env id1
- in
- (body_ty, body_env1 `bothEnv` rhs_env1, Let (NonRec id2 rhs') body')
+-- pprTrace "dmdLet" (ppr id <+> ppr (sig,rhs_env))
+ (body_ty2, Let (NonRec id2 rhs') body')
dmdAnal sigs dmd (Let (Rec pairs) body)
= let
- bndrs = map fst pairs
- (sigs', rhs_envs, pairs') = dmdFix sigs pairs
- (body_ty, body_env, body') = dmdAnal sigs' dmd body
-
- weakened_rhs_envs = zipWithEqual "dmdAnal:Let" (weaken body_env) bndrs rhs_envs
- -- I saw occasions where it was really worth using the
- -- call demands on the Ids to propagate demand info
- -- on the free variables. An example is 'roll' in imaginary/wheel-sieve2
- -- Something like this:
- -- roll x = letrec go y = if ... then roll (x-1) else x+1
- -- in go ms
- -- We want to see that this is strict in x.
-
- rhs_env1 = foldr1 bothEnv weakened_rhs_envs
-
- result_env = delDmdEnvList (body_env `bothEnv` rhs_env1) bndrs
+ bndrs = map fst pairs
+ (sigs', lazy_fv, pairs') = dmdFix NotTopLevel sigs pairs
+ (body_ty, body') = dmdAnal sigs' dmd body
+ body_ty1 = addLazyFVs body_ty lazy_fv
+ in
+ sigs' `seq` body_ty `seq`
+ let
+ (body_ty2, _) = annotateBndrs body_ty1 bndrs
-- Don't bother to add demand info to recursive
-- binders as annotateBndr does;
-- being recursive, we can't treat them strictly.
-- But we do need to remove the binders from the result demand env
in
- (body_ty, result_env, Let (Rec pairs') body')
-\end{code}
+ (body_ty2, Let (Rec pairs') body')
+
-\begin{code}
dmdAnalAlt sigs dmd (con,bndrs,rhs)
= let
- (rhs_ty, rhs_env, rhs') = dmdAnal sigs dmd rhs
- (alt_env, bndrs') = annotateBndrs rhs_env bndrs
+ (rhs_ty, rhs') = dmdAnal sigs dmd rhs
+ (alt_ty, bndrs') = annotateBndrs rhs_ty bndrs
in
- (rhs_ty, alt_env, (con, bndrs', rhs'))
+ (alt_ty, (con, bndrs', rhs'))
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-dmdFix :: SigEnv -- Does not include bindings for this binding
+dmdFix :: TopLevelFlag
+ -> SigEnv -- Does not include bindings for this binding
-> [(Id,CoreExpr)]
- -> (SigEnv,
- [DmdEnv], -- Demands from RHSs
+ -> (SigEnv, DmdEnv,
[(Id,CoreExpr)]) -- Binders annotated with stricness info
-dmdFix sigs pairs
- = loop (map initial_sig pairs) pairs
+dmdFix top_lvl sigs pairs
+ = loop 1 initial_sigs pairs
where
- loop id_sigs pairs
- | id_sigs == id_sigs' = (sigs', rhs_envs, pairs')
- | otherwise = loop id_sigs' pairs'
+ bndrs = map fst pairs
+ initial_sigs = extendSigEnvList sigs [(id, (initial_sig 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')
+ -- 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
+ [ 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')
where
- extra_sigs = [(id,sig) | ((id,_),sig) <- pairs `zip` id_sigs]
- sigs' = extendSigEnvList sigs extra_sigs
- (id_sigs', rhs_envs, pairs') = unzip3 (map (downRhs sigs') pairs)
+ -- 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
+ ((sigs',lazy_fv), pairs') = mapAccumL (my_downRhs top_lvl) (sigs, emptyDmdEnv) pairs
+
+ my_downRhs top_lvl (sigs,lazy_fv) (id,rhs)
+ = -- pprTrace "downRhs {" (ppr id <+> (ppr old_sig))
+ -- (new_sig `seq`
+ -- pprTrace "downRhsEnd" (ppr id <+> ppr new_sig <+> char '}' )
+ ((sigs', lazy_fv'), pair')
+ -- )
+ where
+ (sigs', lazy_fv1, pair') = downRhs top_lvl sigs (id,rhs)
+ lazy_fv' = plusUFM_C both lazy_fv lazy_fv1
+ old_sig = lookup sigs id
+ new_sig = lookup sigs' id
-- Get an initial strictness signature from the Id
-- itself. That way we make use of earlier iterations
-- of the fixpoint algorithm. (Cunning plan.)
- initial_sig (id,_) = idNewStrictness_maybe id `orElse` botSig
-
-
-downRhs :: SigEnv -> (Id, CoreExpr)
- -> (StrictSig, DmdEnv, (Id, CoreExpr))
--- On the way down, compute a strictness signature
--- for the function. Keep its annotated RHS and dmd env
--- for use on the way up
--- The demand-env is that computed for a vanilla call.
-
-downRhs sigs (id, rhs)
- = (sig, rhs_env, (id', rhs'))
+ -- 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
+
+ same_sig sigs sigs' var = lookup sigs var == lookup sigs' var
+ lookup sigs var = case lookupVarEnv sigs var of
+ Just (sig,_) -> sig
+
+downRhs :: TopLevelFlag
+ -> 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)
+ = (sigs', lazy_fv, (id', rhs'))
where
- arity = idArity id
- (rhs_ty, rhs_env, rhs') = dmdAnal sigs (vanillaCall arity) rhs
- sig = mkStrictSig arity rhs_ty
- id' = id `setIdNewStrictness` sig
+ 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
\end{code}
-
%************************************************************************
%* *
\subsection{Strictness signatures and types}
%************************************************************************
\begin{code}
-data DmdEnv
- = DmdEnv (VarEnv Demand) -- All the explicitly mentioned variables
- Bool -- True <=> all the others are Bot
- -- False <=> all the others are Abs
-
-emptyDmdEnv = DmdEnv emptyVarEnv False
-unitDmdEnv var dmd = DmdEnv (unitVarEnv var dmd) False
-
-lookupDmd :: DmdEnv -> Var -> Demand
-lookupDmd (DmdEnv env bh) var = lookupVarEnv env var `orElse` deflt
- where
- deflt | bh = Bot
- | otherwise = Abs
-
-delDmdEnv :: DmdEnv -> Var -> DmdEnv
-delDmdEnv (DmdEnv env b) var = DmdEnv (env `delVarEnv` var) b
-
-delDmdEnvList :: DmdEnv -> [Var] -> DmdEnv
-delDmdEnvList (DmdEnv env b) vars = DmdEnv (env `delVarEnvList` vars) b
-
-
-blackHoleEnv :: DmdType -> DmdEnv -> DmdEnv
-blackHoleEnv (DmdRes BotRes) (DmdEnv env _) = DmdEnv env True
-blackHoleEnv other env = env
-
-bothEnv (DmdEnv env1 b1) (DmdEnv env2 b2)
- = DmdEnv both_env2 (b1 || b2)
+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)
where
- both_env = plusUFM_C both env1 env2
- both_env1 = modifyEnv b1 Bot env2 env1 both_env
- both_env2 = modifyEnv b2 Bot env1 env2 both_env1
-
-lubEnv (DmdEnv env1 b1) (DmdEnv env2 b2)
- = DmdEnv lub_env2 (b1 && b2)
- where
- lub_env = plusUFM_C lub env1 env2
- lub_env1 = modifyEnv (not b1) Lazy env2 env1 lub_env
- lub_env2 = modifyEnv (not b2) Lazy env1 env2 lub_env1
-
-modifyEnv :: Bool -- No-op if False
- -> Demand -- The zap value
- -> VarEnv Demand -> VarEnv Demand -- Env1 and Env2
- -> VarEnv Demand -> VarEnv Demand -- Transform this env
- -- Zap anything in Env1 but not in Env2
- -- Assume: dom(env) includes dom(Env1) and dom(Env2)
-
-modifyEnv need_to_modify zap_value env1 env2 env
- | need_to_modify = foldr zap env (keysUFM (env1 `minusUFM` env2))
- | otherwise = env
- where
- zap uniq env = addToUFM_Directly env uniq zap_value
-
-annotateBndr :: DmdEnv -> Var -> (DmdEnv, Var)
--- The returned env has the var deleted
--- The returned var is annotated with demand info
-annotateBndr dmd_env var
- | isTyVar var = (dmd_env, var)
- | otherwise = (dmd_env `delDmdEnv` var, setIdNewDemandInfo var (lookupDmd dmd_env var))
+ dmd_ty = DmdType strict_fv lazified_dmds res'
+
+ lazy_fv = filterUFM (not . isStrictDmd) fv
+ strict_fv = filterUFM isStrictDmd fv
+ -- We put the strict FVs in the DmdType of the Id, so
+ -- that at its call sites we unleash demands on its strict fvs.
+ -- An example is 'roll' in imaginary/wheel-sieve2
+ -- Something like this:
+ -- roll x = letrec
+ -- go y = if ... then roll (x-1) else x+1
+ -- in
+ -- go ms
+ -- We want to see that roll is strict in x, which is because
+ -- go is called. So we put the DmdEnv for x in go's DmdType.
+ --
+ -- Another example:
+ -- f :: Int -> Int -> Int
+ -- f x y = let t = x+1
+ -- h z = if z==0 then t else
+ -- if z==1 then x+1 else
+ -- x + h (z-1)
+ -- in
+ -- h y
+ -- Calling h does indeed evaluate x, but we can only see
+ -- that if we unleash a demand on x at the call site for t.
+ --
+ -- Incidentally, here's a place where lambda-lifting h would
+ -- lose the cigar --- we couldn't see the joint strictness in t/x
+ --
+ -- ON THE OTHER HAND
+ -- We don't want to put *all* the fv's from the RHS into the
+ -- 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
+ -- 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
+\end{code}
-annotateBndrs = mapAccumR annotateBndr
+The unpack strategy determines whether we'll *really* unpack the argument,
+or whether we'll just remember its strictness. If unpacking would give
+rise to a *lot* of worker args, we may decide not to unpack after all.
-weaken :: DmdEnv -- How the Id is used in its scope
- -> Id
- -> DmdEnv -- The RHS env for the Id, assuming a vanilla call demand
- -> DmdEnv -- The RHS env given the actual demand
--- Consider let f = \x -> R in B
--- The vanilla call demand is C(V), and that's what we use to
--- compute f's strictness signature. If the *actual* demand on
--- f from B is less than this, we must weaken, or lazify, the
--- demands in R to match this
-
-weaken body_env id rhs_env
- | depth >= idArity id -- Enough demand
- = rhs_env
- | otherwise -- Not enough demand
- = lazify rhs_env
+\begin{code}
+setUnpackStrategy :: [Demand] -> [Demand]
+setUnpackStrategy ds
+ = snd (go (opt_MaxWorkerArgs - nonAbsentArgs ds) ds)
where
- (depth,_) = splitCallDmd (lookupDmd body_env id)
-
-lazify (DmdEnv env _) = DmdEnv (mapVarEnv (\_ -> Lazy) env) False
+ go :: Int -- Max number of args available for sub-components of [Demand]
+ -> [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
+ 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
+ non_abs_args = nonAbsentArgs cs
+ -- Delete # of non-absent args to which we'll now be committed
+
+ go n (d:ds) = d `cons` go n ds
+ go n [] = (n,[])
+
+ cons d (n,ds) = (n, d:ds)
+
+nonAbsentArgs :: [Demand] -> Int
+nonAbsentArgs [] = 0
+nonAbsentArgs (Abs : ds) = nonAbsentArgs ds
+nonAbsentArgs (d : ds) = 1 + nonAbsentArgs ds
\end{code}
+
%************************************************************************
%* *
-\subsection{Demand types}
+\subsection{Strictness signatures and types}
%* *
%************************************************************************
\begin{code}
splitDmdTy :: DmdType -> (Demand, DmdType)
-- Split off one function argument
-splitDmdTy (DmdFun dmd res_ty) = (dmd, res_ty)
-splitDmdTy (DmdRes TopRes) = (topDmd, topDmdType)
-splitDmdTy (DmdRes BotRes) = (Abs, DmdRes BotRes)
+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 (DmdRes RetCPR) = panic "splitDmdTy"
+splitDmdTy (DmdType fv [] RetCPR) = panic "splitDmdTy"
+\end{code}
--------------------------
-dmdTypeRes :: DmdType -> Result
-dmdTypeRes (DmdFun dmd res_ty) = dmdTypeRes res_ty
-dmdTypeRes (DmdRes res) = res
+\begin{code}
+unitVarDmd var dmd = DmdType (unitVarEnv var dmd) [] TopRes
--------------------------
-lubDmdTy :: DmdType -> DmdType -> DmdType
-lubDmdTy (DmdFun d1 t1) (DmdFun d2 t2) = DmdFun (d1 `lub` d2) (t1 `lubDmdTy` t2)
-lubDmdTy (DmdRes r1) (DmdRes r2) = DmdRes (r1 `lubRes` r2)
-lubDmdTy t1 t2 = topDmdType
+addVarDmd top_lvl dmd_ty@(DmdType fv ds res) var dmd
+ | isTopLevel top_lvl = dmd_ty -- Don't record top level things
+ | otherwise = DmdType (extendVarEnv fv var dmd) ds res
--------------------------
-lubRes BotRes r = r
-lubRes r BotRes = r
-lubRes RetCPR RetCPR = RetCPR
-lubRes r1 r2 = TopRes
-\end{code}
+addLazyFVs (DmdType fv ds res) lazy_fvs
+ = DmdType (plusUFM_C both fv lazy_fvs) ds res
+annotateBndr :: DmdType -> Var -> (DmdType, Var)
+-- The returned env has the var deleted
+-- The returned var is annotated with demand info
+-- No effect on the argument demands
+annotateBndr dmd_ty@(DmdType fv ds res) var
+ | isTyVar var = (dmd_ty, var)
+ | otherwise = (DmdType fv' ds res, setIdNewDemandInfo var dmd)
+ where
+ (fv', dmd) = removeFV fv var res
+
+annotateBndrs = mapAccumR annotateBndr
+
+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)
+ where
+ (fv', dmd) = removeFV fv id res
+
+removeFV fv var res = (fv', dmd)
+ where
+ fv' = fv `delVarEnv` var
+ dmd = lookupVarEnv fv var `orElse` deflt
+ deflt | isBotRes res = Bot
+ | otherwise = Abs
+\end{code}
%************************************************************************
%* *
%************************************************************************
\begin{code}
-type SigEnv = VarEnv StrictSig
+type SigEnv = VarEnv (StrictSig, TopLevelFlag)
+ -- We use the SigEnv to tell us whether to
+ -- record info about a variable in the DmdEnv
+ -- We do so if it's a LocalId, but not top-level
+ --
+ -- The DmdEnv gives the demand on the free vars of the function
+ -- when it is given enough args to satisfy the strictness signature
+
emptySigEnv = emptyVarEnv
-extendSigEnv = extendVarEnv
+
+extendSigEnv :: TopLevelFlag -> SigEnv -> Id -> StrictSig -> SigEnv
+extendSigEnv top_lvl env var sig = extendVarEnv env var (sig, top_lvl)
+
extendSigEnvList = extendVarEnvList
-lookupSig sigs v = case lookupVarEnv sigs v of
- Just sig -> Just sig
- Nothing -> idNewStrictness_maybe v
dmdTransform :: SigEnv -- The strictness environment
-> Id -- The function
-> Demand -- The demand on the function
-> DmdType -- The demand type of the function in this context
+ -- Returned DmdEnv includes the demand on
+ -- this function plus demand on its free variables
dmdTransform sigs var dmd
- | isDataConId var, -- Data constructor
- Seq k ds <- res_dmd, -- and the demand looks inside its fields
- StrictSig arity dmd_ty <- idNewStrictness var, -- It must have a strictness sig
- length ds == arity -- It's saturated
- = mkDmdFun ds (dmdTypeRes dmd_ty)
- -- Need to extract whether it's a product
-
- | Just (StrictSig arity dmd_ty) <- lookupSig sigs var,
- arity <= depth -- Saturated function;
- = dmd_ty -- Unleash the demand!
+------ 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
+ else
+ topDmdType
+
+------ IMPORTED FUNCTION
+ | isGlobalId var, -- Imported function
+ let StrictSig dmd_ty = getNewStrictness var
+ = if dmdTypeDepth dmd_ty <= call_depth then -- Saturated, so unleash the demand
+ dmd_ty
+ else
+ topDmdType
+
+------ LOCAL LET/REC BOUND THING
+ | Just (StrictSig dmd_ty, top_lvl) <- lookupVarEnv sigs var
+ = let
+ fn_ty | dmdTypeDepth dmd_ty <= call_depth = dmd_ty
+ | otherwise = deferType dmd_ty
+ -- NB: it's important to use deferType, and not just return topDmdType
+ -- Consider let { f x y = p + x } in f 1
+ -- The application isn't saturated, but we must nevertheless propagate
+ -- a lazy demand for p!
+ in
+ addVarDmd top_lvl fn_ty var dmd
+------ LOCAL NON-LET/REC BOUND THING
| otherwise -- Default case
- = topDmdType
+ = unitVarDmd var dmd
where
- (depth, res_dmd) = splitCallDmd dmd
-
-betterStrict :: StrictSig -> StrictSig -> Bool
-betterStrict (StrictSig ar1 t1) (StrictSig ar2 t2)
- = (ar1 >= ar2) && (t1 `betterDmdType` t2)
-
-betterDmdType t1 t2 = (t1 `lubDmdTy` t2) == t2
+ (call_depth, res_dmd) = splitCallDmd dmd
\end{code}
vanillaCall 0 = Eval
vanillaCall n = Call (vanillaCall (n-1))
------------------------------------
+deferType :: DmdType -> DmdType
+deferType (DmdType fv _ _) = DmdType (mapVarEnv defer 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.
+
+defer :: Demand -> Demand
+-- c.f. `lub` Abs
+defer Abs = Abs
+defer (Seq k _ ds) = Seq k Defer ds
+defer other = Lazy
+
+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)
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{LUB and BOTH}
+%* *
+%************************************************************************
+
+\begin{code}
lub :: Demand -> Demand -> Demand
lub Bot d = d
lub Err Bot = Err
lub Err d = d
-lub Abs Bot = Abs
-lub Abs Err = Abs
-lub Abs Abs = Abs
-lub Abs 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 ds) = Seq Keep ds
-lub Eval d = Eval
+lub Eval Abs = Lazy
+lub Eval Lazy = Lazy
+lub Eval (Seq k Now ds) = Seq Keep Now ds
+lub Eval (Seq k Defer ds) = Lazy
+lub Eval d = Eval
lub (Call d1) (Call d2) = Call (lub d1 d2)
-lub (Seq k1 ds1) (Seq k2 ds2) = Seq (k1 `vee` k2)
- (zipWithEqual "lub" lub ds1 ds2)
+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 $$ ppr d2)
-lub d1 d2 = lub d2 d1
+lub d1@(Call _) d2@(Seq _ _ _) = pprPanic "lub" (ppr d1 $$ 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)}
+-- in the result env.
+lubType (DmdType fv1 ds1 r1) (DmdType fv2 ds2 r2)
+ = DmdType lub_fv2 (zipWith lub 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 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
-----------------------------------
both :: Demand -> Demand -> Demand
-both Bot d = Bot
+-- 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 Bot = Bot
both Abs d = d
-both Err Bot = Bot
+both Err Bot = Err
both Err Abs = Err
both Err d = d
-both Lazy Bot = Bot
-both Lazy Abs = Lazy
-both Lazy Err = Lazy
-both Lazy (Seq k ds) = Seq Keep ds
-both Lazy d = d
-
-both Eval Bot = Bot
-both Eval (Seq k ds) = Seq Keep ds
-both Eval (Call d) = Call d
-both Eval d = Eval
-
-both (Seq k1 ds1) (Seq k2 ds2) = Seq (k1 `vee` k2)
- (zipWithEqual "both" both ds1 ds2)
+both Lazy Bot = Lazy
+both Lazy Abs = Lazy
+both Lazy Err = Lazy
+both Lazy (Seq k l ds) = Seq Keep l ds
+both Lazy d = d
+ -- Notice that the Seq case ensures that we have the
+ -- boxed value. The equation originally said
+ -- both (Seq k Now ds) = Seq Keep Now ds
+ -- but it's important that the Keep is switched on even
+ -- for a deferred demand. Otherwise a (Seq Drop Now [])
+ -- might both'd with the result, and then we won't pass
+ -- the boxed value. Here's an example:
+ -- (x-1) `seq` (x+1, x)
+ -- From the (x+1, x) we get (U*(V) `both` L), which must give S*(V)
+ -- From (x-1) we get U(V). Combining, we must get S(V).
+ -- If we got U*(V) from the pair, we'd end up with U(V), and that
+ -- can be a disaster if a component of the data structure is absent.
+ -- [Disaster = enter an absent argument.]
+
+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 $$ ppr d2)
-both d1 d2 = both d2 d1
+both d1@(Call _) d2@(Seq _ _ _) = pprPanic "both" (ppr d1 $$ ppr d2)
+both d1 d2 = both d2 d1
-betterDemand :: Demand -> Demand -> Bool
--- If d1 `better` d2, and d2 `better` d2, then d1==d2
-betterDemand d1 d2 = (d1 `lub` d2) == d2
+-----------------------------------
+-- 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
+
+-----------------------------------
+-- (t1 `bothType` t2) takes the argument/result info from t1,
+-- using t2 just for its free-var info
+bothType (DmdType fv1 ds1 r1) (DmdType fv2 ds2 r2)
+ = DmdType both_fv2 ds1 r1
+ where
+ both_fv = plusUFM_C both fv1 fv2
+ both_fv1 = modifyEnv (isBotRes r1) (`both` Bot) fv2 fv1 both_fv
+ both_fv2 = modifyEnv (isBotRes r2) (`both` Bot) fv1 fv2 both_fv1
+ -- both is the identity for Abs
+\end{code}
+
+\begin{code}
+modifyEnv :: Bool -- No-op if False
+ -> (Demand -> Demand) -- The zapper
+ -> DmdEnv -> DmdEnv -- Env1 and Env2
+ -> DmdEnv -> DmdEnv -- Transform this env
+ -- Zap anything in Env1 but not in Env2
+ -- Assume: dom(env) includes dom(Env1) and dom(Env2)
+
+modifyEnv need_to_modify zapper env1 env2 env
+ | need_to_modify = foldr zap env (keysUFM (env1 `minusUFM` env2))
+ | otherwise = env
+ where
+ zap uniq env = addToUFM_Directly env uniq (zapper current_val)
+ where
+ current_val = expectJust "modifyEnv" (lookupUFM_Directly env uniq)
\end{code}
\begin{code}
--- Move these to Id.lhs
-idNewStrictness_maybe :: Id -> Maybe StrictSig
-idNewStrictness :: Id -> StrictSig
-
-idNewStrictness_maybe id = newStrictnessInfo (idInfo id)
-idNewStrictness id = idNewStrictness_maybe id `orElse` topSig
-
-setIdNewStrictness :: Id -> StrictSig -> Id
-setIdNewStrictness id sig = modifyIdInfo (`setNewStrictnessInfo` sig) id
-
-idNewDemandInfo :: Id -> Demand
-idNewDemandInfo id = newDemandInfo (idInfo id)
-
-setIdNewDemandInfo :: Id -> Demand -> Id
-setIdNewDemandInfo id dmd = modifyIdInfo (`setNewDemandInfo` dmd) id
-\end{code}
-
-\begin{code}
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) = get_changes_var id $$ get_changes_expr rhs
+get_changes_pr (id,rhs)
+ | isImplicitId id = empty -- We don't look inside these
+ | otherwise = get_changes_var id $$ get_changes_expr rhs
get_changes_var var
| isId var = get_changes_str var $$ get_changes_dmd var
get_changes_expr (Lit l) = empty
get_changes_expr (Note n e) = get_changes_expr e
get_changes_expr (App e1 e2) = get_changes_expr e1 $$ get_changes_expr e2
-get_changes_expr (Lam b e) = get_changes_var b $$ get_changes_expr e
+get_changes_expr (Lam b e) = {- get_changes_var b $$ -} get_changes_expr e
get_changes_expr (Let b e) = get_changes_bind b $$ get_changes_expr e
-get_changes_expr (Case e b a) = get_changes_expr e $$ get_changes_var b $$ vcat (map get_changes_alt a)
+get_changes_expr (Case e b a) = get_changes_expr e $$ {- get_changes_var b $$ -} vcat (map get_changes_alt a)
-get_changes_alt (con,bs,rhs) = vcat (map get_changes_var bs) $$ get_changes_expr rhs
+get_changes_alt (con,bs,rhs) = {- vcat (map get_changes_var bs) $$ -} get_changes_expr rhs
get_changes_str id
| new_better && old_better = empty
where
message word = text word <+> text "strictness for" <+> ppr id <+> info
info = (text "Old" <+> ppr old) $$ (text "New" <+> ppr new)
- new = idNewStrictness id
- old = mkNewStrictnessInfo (idArity id) (idStrictness id) (idCprInfo id)
- old_better = old `betterStrict` new
- new_better = new `betterStrict` old
+ new = squashDmdEnv (idNewStrictness id) -- Don't report diffs in the env
+ old = newStrictnessFromOld id
+ old_better = old `betterStrictness` new
+ new_better = new `betterStrictness` old
get_changes_dmd id
+ | isUnLiftedType (idType id) = empty -- Not useful
| new_better && old_better = empty
| new_better = message "BETTER"
| old_better = message "WORSE"
where
message word = text word <+> text "demand for" <+> ppr id <+> info
info = (text "Old" <+> ppr old) $$ (text "New" <+> ppr new)
- new = idNewDemandInfo id
+ new = lazify (idNewDemandInfo id) -- Lazify to avoid spurious improvements
old = newDemand (idDemandInfo id)
new_better = new `betterDemand` old
old_better = old `betterDemand` new
-#endif /* DEBUG */
\end{code}
-
projects / ghc-hetmet.git / blobdiff