import Demand -- All of it
import CoreSyn
import PprCore
+import Coercion ( isCoVarType )
import CoreUtils ( exprIsHNF, exprIsTrivial )
import CoreArity ( exprArity )
import DataCon ( dataConTyCon, dataConRepStrictness )
import TyCon ( isProductTyCon, isRecursiveTyCon )
import Id ( Id, idType, idInlineActivation,
isDataConWorkId, isGlobalId, idArity,
- idStrictness, idStrictness_maybe,
+ idStrictness,
setIdStrictness, idDemandInfo, idUnfolding,
- idDemandInfo_maybe,
- setIdDemandInfo
+ idDemandInfo_maybe, setIdDemandInfo
)
-import Var ( Var )
+import Var ( Var, isTyVar )
import VarEnv
import TysWiredIn ( unboxedPairDataCon )
import TysPrim ( realWorldStatePrimTy )
import UniqFM ( addToUFM_Directly, lookupUFM_Directly,
- minusUFM, ufmToList, filterUFM )
-import Type ( isUnLiftedType, coreEqType, splitTyConApp_maybe )
+ minusUFM, filterUFM )
+import Type ( isUnLiftedType, eqType, splitTyConApp_maybe )
import Coercion ( coercionKind )
import Util ( mapAndUnzip, lengthIs, zipEqual )
import BasicTypes ( Arity, TopLevelFlag(..), isTopLevel, isNeverActive,
RecFlag(..), isRec, isMarkedStrict )
import Maybes ( orElse, expectJust )
import Outputable
+import Pair
import Data.List
+import FastString
\end{code}
To think about
-> CoreBind
-> (SigEnv, CoreBind)
dmdAnalTopBind sigs (NonRec id rhs)
- = let
- ( _, _, (_, 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
- (sigs2, NonRec id2 rhs2)
+ = (sigs2, NonRec id2 rhs2)
+ where
+ ( _, _, (_, rhs1)) = dmdAnalRhs TopLevel NonRecursive (virgin sigs) (id, rhs)
+ (sigs2, _, (id2, rhs2)) = dmdAnalRhs TopLevel NonRecursive (nonVirgin sigs) (id, rhs1)
+ -- Do two passes to improve CPR information
+ -- See comments with ignore_cpr_info in mk_sig_ty
+ -- and with extendSigsWithLam
dmdAnalTopBind sigs (Rec pairs)
- = let
- (sigs', _, pairs') = dmdFix TopLevel sigs pairs
+ = (sigs', Rec pairs')
+ where
+ (sigs', _, pairs') = dmdFix TopLevel (virgin 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)
+-- b) the unfolding (decorated with strictness 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
+ (_, rhs1) = dmdAnal (virgin emptySigEnv) call_dmd rhs
+ (rhs_ty, rhs2) = dmdAnal (nonVirgin 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
%************************************************************************
\begin{code}
-dmdAnal :: SigEnv -> Demand -> CoreExpr -> (DmdType, CoreExpr)
+dmdAnal :: AnalEnv -> Demand -> CoreExpr -> (DmdType, CoreExpr)
dmdAnal _ Abs e = (topDmdType, e)
-dmdAnal sigs dmd e
+dmdAnal env dmd e
| not (isStrictDmd dmd)
= let
- (res_ty, e') = dmdAnal sigs evalDmd e
+ (res_ty, e') = dmdAnal env evalDmd e
in
(deferType res_ty, e')
-- It's important not to analyse e with a lazy demand because
dmdAnal _ _ (Lit lit) = (topDmdType, Lit lit)
dmdAnal _ _ (Type ty) = (topDmdType, Type ty) -- Doesn't happen, in fact
+dmdAnal _ _ (Coercion co) = (topDmdType, Coercion co)
-dmdAnal sigs dmd (Var var)
- = (dmdTransform sigs var dmd, Var var)
+dmdAnal env dmd (Var var)
+ = (dmdTransform env var dmd, Var var)
-dmdAnal sigs dmd (Cast e co)
+dmdAnal env dmd (Cast e co)
= (dmd_ty, Cast e' co)
where
- (dmd_ty, e') = dmdAnal sigs dmd' e
- to_co = snd (coercionKind co)
+ (dmd_ty, e') = dmdAnal env dmd' e
+ to_co = pSnd (coercionKind co)
dmd'
| Just (tc, _) <- splitTyConApp_maybe to_co
, isRecursiveTyCon tc = evalDmd
-- inside recursive products -- we might not reach
-- a fixpoint. So revert to a vanilla Eval demand
-dmdAnal sigs dmd (Note n e)
+dmdAnal env dmd (Note n e)
= (dmd_ty, Note n e')
where
- (dmd_ty, e') = dmdAnal sigs dmd e
+ (dmd_ty, e') = dmdAnal env dmd e
-dmdAnal sigs dmd (App fun (Type ty))
+dmdAnal env dmd (App fun (Type ty))
= (fun_ty, App fun' (Type ty))
where
+ (fun_ty, fun') = dmdAnal env dmd fun
+
+dmdAnal sigs dmd (App fun (Coercion co))
+ = (fun_ty, App fun' (Coercion co))
+ where
(fun_ty, fun') = dmdAnal sigs dmd fun
-- Lots of the other code is there to make this
-- beautiful, compositional, application rule :-)
-dmdAnal sigs dmd (App fun arg) -- Non-type arguments
+dmdAnal env dmd (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
+ (fun_ty, fun') = dmdAnal env (Call dmd) fun
+ (arg_ty, arg') = dmdAnal env arg_dmd arg
(arg_dmd, res_ty) = splitDmdTy fun_ty
in
(res_ty `bothType` arg_ty, App fun' arg')
-dmdAnal sigs dmd (Lam var body)
- | isTyCoVar var
+dmdAnal env dmd (Lam var body)
+ | isTyVar var
= let
- (body_ty, body') = dmdAnal sigs dmd body
+ (body_ty, body') = dmdAnal env dmd body
in
(body_ty, Lam var body')
| Call body_dmd <- dmd -- A call demand: good!
= let
- sigs' = extendSigsWithLam sigs var
- (body_ty, body') = dmdAnal sigs' body_dmd body
- (lam_ty, var') = annotateLamIdBndr sigs body_ty var
+ env' = extendSigsWithLam env var
+ (body_ty, body') = dmdAnal env' body_dmd body
+ (lam_ty, var') = annotateLamIdBndr env 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 evalDmd body
- (lam_ty, var') = annotateLamIdBndr sigs body_ty var
+ (body_ty, body') = dmdAnal env evalDmd body
+ (lam_ty, var') = annotateLamIdBndr env body_ty var
in
(deferType lam_ty, Lam var' body')
-dmdAnal sigs dmd (Case scrut case_bndr ty [alt@(DataAlt dc, _, _)])
+dmdAnal env dmd (Case scrut case_bndr ty [alt@(DataAlt dc, _, _)])
| let tycon = dataConTyCon dc
, isProductTyCon tycon
, not (isRecursiveTyCon tycon)
= let
- sigs_alt = extendSigEnv NotTopLevel sigs case_bndr case_bndr_sig
- (alt_ty, alt') = dmdAnalAlt sigs_alt dmd alt
+ env_alt = extendAnalEnv NotTopLevel env case_bndr case_bndr_sig
+ (alt_ty, alt') = dmdAnalAlt env_alt dmd alt
(alt_ty1, case_bndr') = annotateBndr alt_ty case_bndr
(_, bndrs', _) = alt'
case_bndr_sig = cprSig
scrut_dmd = alt_dmd `both`
idDemandInfo case_bndr'
- (scrut_ty, scrut') = dmdAnal sigs scrut_dmd scrut
+ (scrut_ty, scrut') = dmdAnal env scrut_dmd scrut
in
(alt_ty1 `bothType` scrut_ty, Case scrut' case_bndr' ty [alt'])
-dmdAnal sigs dmd (Case scrut case_bndr ty alts)
+dmdAnal env dmd (Case scrut case_bndr ty alts)
= let
- (alt_tys, alts') = mapAndUnzip (dmdAnalAlt sigs dmd) alts
- (scrut_ty, scrut') = dmdAnal sigs evalDmd scrut
+ (alt_tys, alts') = mapAndUnzip (dmdAnalAlt env dmd) alts
+ (scrut_ty, scrut') = dmdAnal env 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' ty alts')
-dmdAnal sigs dmd (Let (NonRec id rhs) body)
+dmdAnal env dmd (Let (NonRec id rhs) body)
= let
- (sigs', lazy_fv, (id1, rhs')) = dmdAnalRhs NotTopLevel NonRecursive sigs (id, rhs)
- (body_ty, body') = dmdAnal sigs' dmd body
+ (sigs', lazy_fv, (id1, rhs')) = dmdAnalRhs NotTopLevel NonRecursive env (id, rhs)
+ (body_ty, body') = dmdAnal (updSigEnv env sigs') dmd body
(body_ty1, id2) = annotateBndr body_ty id1
body_ty2 = addLazyFVs body_ty1 lazy_fv
in
-- bother to re-analyse the RHS.
(body_ty2, Let (NonRec id2 rhs') body')
-dmdAnal sigs dmd (Let (Rec pairs) body)
+dmdAnal env dmd (Let (Rec pairs) body)
= let
bndrs = map fst pairs
- (sigs', lazy_fv, pairs') = dmdFix NotTopLevel sigs pairs
- (body_ty, body') = dmdAnal sigs' dmd body
+ (sigs', lazy_fv, pairs') = dmdFix NotTopLevel env pairs
+ (body_ty, body') = dmdAnal (updSigEnv env sigs') dmd body
body_ty1 = addLazyFVs body_ty lazy_fv
in
sigs' `seq` body_ty `seq`
(body_ty2, Let (Rec pairs') body')
-dmdAnalAlt :: SigEnv -> Demand -> Alt Var -> (DmdType, Alt Var)
-dmdAnalAlt sigs dmd (con,bndrs,rhs)
+dmdAnalAlt :: AnalEnv -> Demand -> Alt Var -> (DmdType, Alt Var)
+dmdAnalAlt env dmd (con,bndrs,rhs)
= let
- (rhs_ty, rhs') = dmdAnal sigs dmd rhs
+ (rhs_ty, rhs') = dmdAnal env dmd rhs
rhs_ty' = addDataConPatDmds con bndrs rhs_ty
(alt_ty, bndrs') = annotateBndrs rhs_ty' bndrs
final_alt_ty | io_hack_reqd = alt_ty `lubType` topDmdType
-- ; print len }
io_hack_reqd = con == DataAlt unboxedPairDataCon &&
- idType (head bndrs) `coreEqType` realWorldStatePrimTy
+ idType (head bndrs) `eqType` realWorldStatePrimTy
in
(final_alt_ty, (con, bndrs', rhs'))
is even more important. We don't want the wrapper to rebox an unboxed
argument, and pass an Int to $wfoo!
+
+%************************************************************************
+%* *
+ Demand transformer
+%* *
+%************************************************************************
+
+\begin{code}
+dmdTransform :: AnalEnv -- 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 env var dmd
+
+------ DATA CONSTRUCTOR
+ | isDataConWorkId var -- Data constructor
+ = let
+ StrictSig dmd_ty = idStrictness 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
+ _ -> 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 = idStrictness var
+ = -- pprTrace "strict-sig" (ppr var $$ ppr dmd_ty) $
+ 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) <- lookupSigEnv env 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
+ if isTopLevel top_lvl then fn_ty -- Don't record top level things
+ else addVarDmd fn_ty var dmd
+
+------ LOCAL NON-LET/REC BOUND THING
+ | otherwise -- Default case
+ = unitVarDmd var dmd
+
+ where
+ (call_depth, res_dmd) = splitCallDmd dmd
+\end{code}
+
%************************************************************************
%* *
\subsection{Bindings}
\begin{code}
dmdFix :: TopLevelFlag
- -> SigEnv -- Does not include bindings for this binding
+ -> AnalEnv -- Does not include bindings for this binding
-> [(Id,CoreExpr)]
-> (SigEnv, DmdEnv,
[(Id,CoreExpr)]) -- Binders annotated with stricness info
-dmdFix top_lvl sigs orig_pairs
- = loop 1 initial_sigs orig_pairs
+dmdFix top_lvl env orig_pairs
+ = loop 1 initial_env orig_pairs
where
bndrs = map fst orig_pairs
- initial_sigs = extendSigEnvList sigs [(id, (initialSig id, top_lvl)) | id <- bndrs]
+ initial_env = addInitialSigs top_lvl env bndrs
loop :: Int
- -> SigEnv -- Already contains the current sigs
+ -> AnalEnv -- Already contains the current sigs
-> [(Id,CoreExpr)]
-> (SigEnv, DmdEnv, [(Id,CoreExpr)])
- loop n sigs pairs
+ loop n env pairs
+ = -- pprTrace "dmd loop" (ppr n <+> ppr bndrs $$ ppr env) $
+ loop' n env pairs
+
+ loop' n env pairs
| found_fixpoint
= (sigs', lazy_fv, pairs')
- -- Note: use pairs', not pairs. pairs' is the result of
+ -- Note: return 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 >= 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:" <+> 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'
+ | n >= 10
+ = pprTrace "dmdFix loop" (ppr n <+> (vcat
+ [ text "Sigs:" <+> ppr [ (id,lookupVarEnv sigs id, lookupVarEnv sigs' id)
+ | (id,_) <- pairs],
+ text "env:" <+> ppr env,
+ text "binds:" <+> pprCoreBinding (Rec pairs)]))
+ (sigEnv env, 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) (nonVirgin sigs') pairs'
where
+ sigs = sigEnv env
found_fixpoint = all (same_sig sigs sigs') bndrs
- -- Use the new signature to do the next pair
+
+ ((sigs',lazy_fv), pairs') = mapAccumL my_downRhs (sigs, emptyDmdEnv) pairs
+ -- mapAccumL: 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') = dmdAnalRhs top_lvl Recursive sigs (id,rhs)
- lazy_fv' = plusVarEnv_C both lazy_fv lazy_fv1
- -- old_sig = lookup sigs id
- -- new_sig = lookup sigs' id
+ my_downRhs (sigs,lazy_fv) (id,rhs)
+ = ((sigs', lazy_fv'), pair')
+ where
+ (sigs', lazy_fv1, pair') = dmdAnalRhs top_lvl Recursive (updSigEnv env sigs) (id,rhs)
+ lazy_fv' = plusVarEnv_C both lazy_fv lazy_fv1
same_sig sigs sigs' var = lookup sigs var == lookup sigs' var
lookup sigs var = case lookupVarEnv sigs var of
Just (sig,_) -> sig
Nothing -> pprPanic "dmdFix" (ppr var)
- -- 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
-initialSig :: Id -> StrictSig
-initialSig id = idStrictness_maybe id `orElse` botSig
-
dmdAnalRhs :: TopLevelFlag -> RecFlag
- -> SigEnv -> (Id, CoreExpr)
+ -> AnalEnv -> (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.
-dmdAnalRhs top_lvl rec_flag sigs (id, rhs)
+dmdAnalRhs top_lvl rec_flag env (id, rhs)
= (sigs', lazy_fv, (id', rhs'))
where
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
+ (rhs_dmd_ty, rhs') = dmdAnal env (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 `setIdStrictness` sig_ty
- sigs' = extendSigEnv top_lvl sigs id sig_ty
+ sigs' = extendSigEnv top_lvl (sigEnv env) id sig_ty
\end{code}
+
%************************************************************************
%* *
\subsection{Strictness signatures and types}
-- The returned var is annotated with demand info
-- No effect on the argument demands
annotateBndr dmd_ty@(DmdType fv ds res) var
- | isTyCoVar var = (dmd_ty, var)
+ | isTyVar var = (dmd_ty, var)
| otherwise = (DmdType fv' ds res, setIdDemandInfo var dmd)
where
(fv', dmd) = removeFV fv var res
annotateBndrs :: DmdType -> [Var] -> (DmdType, [Var])
annotateBndrs = mapAccumR annotateBndr
-annotateLamIdBndr :: SigEnv
+annotateLamIdBndr :: AnalEnv
-> DmdType -- Demand type of body
-> Id -- Lambda binder
-> (DmdType, -- Demand type of lambda
Id) -- and binder annotated with demand
-annotateLamIdBndr sigs (DmdType fv ds res) id
+annotateLamIdBndr env (DmdType fv ds res) id
-- For lambdas we add the demand to the argument demands
-- Only called for Ids
= ASSERT( isId id )
Nothing -> main_ty
Just unf -> main_ty `bothType` unf_ty
where
- (unf_ty, _) = dmdAnal sigs dmd unf
+ (unf_ty, _) = dmdAnal env dmd unf
main_ty = DmdType fv' (hacked_dmd:ds) res
zapUnlifted :: Id -> Demand -> Demand
-- For unlifted-type variables, we are only
-- interested in Bot/Abs/Box Abs
-zapUnlifted _ Bot = Bot
-zapUnlifted _ Abs = Abs
-zapUnlifted id dmd | isUnLiftedType (idType id) = lazyDmd
- | otherwise = dmd
+zapUnlifted id dmd
+ = case dmd of
+ _ | isCoVarType ty -> lazyDmd -- For coercions, ignore str/abs totally
+ Bot -> Bot
+ Abs -> Abs
+ _ | isUnLiftedType ty -> lazyDmd -- For unlifted types, ignore strictness
+ | otherwise -> dmd
+ where
+ ty = idType id
\end{code}
Note [Lamba-bound unfoldings]
%************************************************************************
\begin{code}
-type SigEnv = VarEnv (StrictSig, TopLevelFlag)
- -- We use the SigEnv to tell us whether to
+data AnalEnv
+ = AE { ae_sigs :: SigEnv
+ , ae_virgin :: Bool } -- True on first iteration only
+ -- See Note [Initialising strictness]
+ -- We use the se_env 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
+type SigEnv = VarEnv (StrictSig, TopLevelFlag)
+
+instance Outputable AnalEnv where
+ ppr (AE { ae_sigs = env, ae_virgin = virgin })
+ = ptext (sLit "AE") <+> braces (vcat
+ [ ptext (sLit "ae_virgin =") <+> ppr virgin
+ , ptext (sLit "ae_sigs =") <+> ppr env ])
+
emptySigEnv :: SigEnv
-emptySigEnv = emptyVarEnv
+emptySigEnv = emptyVarEnv
+
+sigEnv :: AnalEnv -> SigEnv
+sigEnv = ae_sigs
+
+updSigEnv :: AnalEnv -> SigEnv -> AnalEnv
+updSigEnv env sigs = env { ae_sigs = sigs }
+
+extendAnalEnv :: TopLevelFlag -> AnalEnv -> Id -> StrictSig -> AnalEnv
+extendAnalEnv top_lvl env var sig
+ = env { ae_sigs = extendSigEnv top_lvl (ae_sigs env) var sig }
extendSigEnv :: TopLevelFlag -> SigEnv -> Id -> StrictSig -> SigEnv
-extendSigEnv top_lvl env var sig = extendVarEnv env var (sig, top_lvl)
+extendSigEnv top_lvl sigs var sig = extendVarEnv sigs var (sig, top_lvl)
+
+lookupSigEnv :: AnalEnv -> Id -> Maybe (StrictSig, TopLevelFlag)
+lookupSigEnv env id = lookupVarEnv (ae_sigs env) id
-extendSigEnvList :: SigEnv -> [(Id, (StrictSig, TopLevelFlag))] -> SigEnv
-extendSigEnvList = extendVarEnvList
+addInitialSigs :: TopLevelFlag -> AnalEnv -> [Id] -> AnalEnv
+-- See Note [Initialising strictness]
+addInitialSigs top_lvl env@(AE { ae_sigs = sigs, ae_virgin = virgin }) ids
+ = env { ae_sigs = extendVarEnvList sigs [ (id, (init_sig id, top_lvl))
+ | id <- ids ] }
+ where
+ init_sig | virgin = \_ -> botSig
+ | otherwise = idStrictness
-extendSigsWithLam :: SigEnv -> Id -> SigEnv
--- Extend the SigEnv when we meet a lambda binder
+virgin, nonVirgin :: SigEnv -> AnalEnv
+virgin sigs = AE { ae_sigs = sigs, ae_virgin = True }
+nonVirgin sigs = AE { ae_sigs = sigs, ae_virgin = False }
+
+extendSigsWithLam :: AnalEnv -> Id -> AnalEnv
+-- Extend the AnalEnv 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],
-- definitely has product type, else we may get over-optimistic
-- CPR results (e.g. from \x -> x!).
-extendSigsWithLam sigs id
+extendSigsWithLam env id
= case idDemandInfo_maybe id of
- Nothing -> extendVarEnv sigs id (cprSig, NotTopLevel)
+ Nothing -> extendAnalEnv NotTopLevel env id cprSig
-- Optimistic in the Nothing case;
-- See notes [CPR-AND-STRICTNESS]
- Just (Eval (Prod _)) -> extendVarEnv sigs id (cprSig, NotTopLevel)
- _ -> sigs
-
-
-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
-
------- DATA CONSTRUCTOR
- | isDataConWorkId var -- Data constructor
- = let
- StrictSig dmd_ty = idStrictness 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
- _ -> 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 = idStrictness var
- = if dmdTypeDepth dmd_ty <= call_depth then -- Saturated, so unleash the demand
- dmd_ty
- else
- topDmdType
+ Just (Eval (Prod _)) -> extendAnalEnv NotTopLevel env id cprSig
+ _ -> env
+\end{code}
------- 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
- if isTopLevel top_lvl then fn_ty -- Don't record top level things
- else addVarDmd fn_ty var dmd
+Note [Initialising strictness]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Our basic plan is to initialise the strictness of each Id in
+a recursive group to "bottom", and find a fixpoint from there.
+However, this group A might be inside an *enclosing* recursive
+group B, in which case we'll do the entire fixpoint shebang on A
+for each iteration of B.
------- LOCAL NON-LET/REC BOUND THING
- | otherwise -- Default case
- = unitVarDmd var dmd
+To speed things up, we initialise each iteration of B from the result
+of the last one, which is neatly recorded in each binder. That way we
+make use of earlier iterations of the fixpoint algorithm. (Cunning
+plan.)
- where
- (call_depth, res_dmd) = splitCallDmd dmd
-\end{code}
+But on the *first* iteration we want to *ignore* the current strictness
+of the Id, and start from "bottom". Nowadays the Id can have a current
+strictness, because interface files record strictness for nested bindings.
+To know when we are in the first iteration, we look at the ae_virgin
+field of the AnalEnv.
%************************************************************************
%* *
-\subsection{Demands}
+ Demands
%* *
%************************************************************************
projects / ghc-hetmet.git / blobdiff