module IdInfo (
IdInfo, -- Abstract
- noIdInfo,
- ppIdInfo,
+ vanillaIdInfo, constantIdInfo, mkIdInfo, seqIdInfo, megaSeqIdInfo,
+
+ -- Zapping
+ zapLamInfo, zapDemandInfo,
+ zapSpecPragInfo, shortableIdInfo, copyIdInfo,
+
+ -- Flavour
+ IdFlavour(..), flavourInfo, makeConstantFlavour,
+ setNoDiscardInfo, setFlavourInfo,
+ ppFlavourInfo,
-- Arity
ArityInfo(..),
- exactArity, atLeastArity, unknownArity,
+ exactArity, atLeastArity, unknownArity, hasArity,
arityInfo, setArityInfo, ppArityInfo, arityLowerBound,
- -- Strictness
- StrictnessInfo(..), -- Non-abstract
- workerExists, mkStrictnessInfo, mkBottomStrictnessInfo,
- noStrictnessInfo, bottomIsGuaranteed, strictnessInfo,
- ppStrictnessInfo, setStrictnessInfo,
+ -- Strictness; imported from Demand
+ StrictnessInfo(..),
+ mkStrictnessInfo, noStrictnessInfo,
+ ppStrictnessInfo,isBottomingStrictness,
+ strictnessInfo, setStrictnessInfo,
+
+ -- Usage generalisation
+ TyGenInfo(..),
+ tyGenInfo, setTyGenInfo,
+ noTyGenInfo, isNoTyGenInfo, ppTyGenInfo, tyGenInfoString,
+
+ -- Worker
+ WorkerInfo(..), workerExists, wrapperArity, workerId,
+ workerInfo, setWorkerInfo, ppWorkerInfo,
-- Unfolding
unfoldingInfo, setUnfoldingInfo,
demandInfo, setDemandInfo,
-- Inline prags
- InlinePragInfo(..), OccInfo(..),
- inlinePragInfo, setInlinePragInfo, notInsideLambda,
+ InlinePragInfo(..),
+ inlinePragInfo, setInlinePragInfo, pprInlinePragInfo,
+ isNeverInlinePrag, neverInlinePrag,
- -- Specialisation
- IdSpecEnv, specInfo, setSpecInfo,
+ -- Occurrence info
+ OccInfo(..), isFragileOcc, isDeadOcc, isLoopBreaker,
+ InsideLam, OneBranch, insideLam, notInsideLam, oneBranch, notOneBranch,
+ occInfo, setOccInfo,
- -- Update
- UpdateInfo, UpdateSpec,
- mkUpdateInfo, updateInfo, updateInfoMaybe, ppUpdateInfo, setUpdateInfo,
+ -- Specialisation
+ specInfo, setSpecInfo,
-- CAF info
- CafInfo(..), cafInfo, setCafInfo, ppCafInfo,
+ CafInfo(..), cafInfo, setCafInfo, mayHaveCafRefs, ppCafInfo,
+
+ -- Constructed Product Result Info
+ CprInfo(..), cprInfo, setCprInfo, ppCprInfo, noCprInfo,
+
+ -- Lambda-bound variable info
+ LBVarInfo(..), lbvarInfo, setLBVarInfo, noLBVarInfo, hasNoLBVarInfo
) where
#include "HsVersions.h"
-import {-# SOURCE #-} CoreUnfold ( Unfolding, noUnfolding )
-import {-# SOURCE #-} CoreSyn ( CoreExpr )
-
-import SpecEnv ( SpecEnv, emptySpecEnv )
-import Demand ( Demand, isLazy, wwLazy, pprDemands )
+import CoreSyn
+import Type ( Type, usOnce )
+import PrimOp ( PrimOp )
+import Var ( Id )
+import BasicTypes ( OccInfo(..), isFragileOcc, isDeadOcc, seqOccInfo, isLoopBreaker,
+ InsideLam, insideLam, notInsideLam,
+ OneBranch, oneBranch, notOneBranch,
+ Arity
+ )
+import DataCon ( DataCon )
+import FieldLabel ( FieldLabel )
+import Type ( usOnce, usMany )
+import Demand -- Lots of stuff
import Outputable
+import Util ( seqList )
+
+infixl 1 `setDemandInfo`,
+ `setTyGenInfo`,
+ `setStrictnessInfo`,
+ `setSpecInfo`,
+ `setArityInfo`,
+ `setInlinePragInfo`,
+ `setUnfoldingInfo`,
+ `setCprInfo`,
+ `setWorkerInfo`,
+ `setLBVarInfo`,
+ `setCafInfo`,
+ `setOccInfo`
+ -- infixl so you can say (id `set` a `set` b)
\end{code}
An @IdInfo@ gives {\em optional} information about an @Id@. If
present it never lies, but it may not be present, in which case there
is always a conservative assumption which can be made.
+ There is one exception: the 'flavour' is *not* optional.
+ You must not discard it.
+ It used to be in Var.lhs, but that seems unclean.
+
Two @Id@s may have different info even though they have the same
@Unique@ (and are hence the same @Id@); for example, one might lack
the properties attached to the other.
The @IdInfo@ gives information about the value, or definition, of the
@Id@. It does {\em not} contain information about the @Id@'s usage
-(except for @DemandInfo@? ToDo).
+(except for @DemandInfo@? ToDo). (@lbvarInfo@ is also a marginal
+case. KSW 1999-04).
\begin{code}
data IdInfo
= IdInfo {
- arityInfo :: ArityInfo, -- Its arity
- demandInfo :: Demand, -- Whether or not it is definitely demanded
- specInfo :: IdSpecEnv, -- Specialisations of this function which exist
- strictnessInfo :: StrictnessInfo, -- Strictness properties
- unfoldingInfo :: Unfolding, -- Its unfolding
- updateInfo :: UpdateInfo, -- Which args should be updated
- cafInfo :: CafInfo,
- inlinePragInfo :: !InlinePragInfo -- Inline pragmas
+ flavourInfo :: IdFlavour, -- NOT OPTIONAL
+ arityInfo :: ArityInfo, -- Its arity
+ demandInfo :: Demand, -- Whether or not it is definitely demanded
+ specInfo :: CoreRules, -- Specialisations of this function which exist
+ tyGenInfo :: TyGenInfo, -- Restrictions on usage-generalisation of this Id
+ strictnessInfo :: StrictnessInfo, -- Strictness properties
+ workerInfo :: WorkerInfo, -- Pointer to Worker Function
+ unfoldingInfo :: Unfolding, -- Its unfolding
+ cafInfo :: CafInfo, -- whether it refers (indirectly) to any CAFs
+ cprInfo :: CprInfo, -- Function always constructs a product result
+ lbvarInfo :: LBVarInfo, -- Info about a lambda-bound variable
+ inlinePragInfo :: InlinePragInfo, -- Inline pragma
+ occInfo :: OccInfo -- How it occurs
}
+
+seqIdInfo :: IdInfo -> ()
+seqIdInfo (IdInfo {}) = ()
+
+megaSeqIdInfo :: IdInfo -> ()
+megaSeqIdInfo info
+ = seqFlavour (flavourInfo info) `seq`
+ seqArity (arityInfo info) `seq`
+ seqDemand (demandInfo info) `seq`
+ seqRules (specInfo info) `seq`
+ seqTyGenInfo (tyGenInfo info) `seq`
+ seqStrictnessInfo (strictnessInfo info) `seq`
+ seqWorker (workerInfo info) `seq`
+
+-- seqUnfolding (unfoldingInfo info) `seq`
+-- Omitting this improves runtimes a little, presumably because
+-- some unfoldings are not calculated at all
+
+ seqCaf (cafInfo info) `seq`
+ seqCpr (cprInfo info) `seq`
+ seqLBVar (lbvarInfo info) `seq`
+ seqOccInfo (occInfo info)
\end{code}
Setters
\begin{code}
-setUpdateInfo ud info = info { updateInfo = ud }
-setDemandInfo dd info = info { demandInfo = dd }
-setStrictnessInfo st info = info { strictnessInfo = st }
-setSpecInfo sp info = info { specInfo = sp }
-setArityInfo ar info = info { arityInfo = ar }
-setInlinePragInfo pr info = info { inlinePragInfo = pr }
-setUnfoldingInfo uf info = info { unfoldingInfo = uf }
-setCafInfo cf info = info { cafInfo = cf }
+setFlavourInfo info fl = fl `seq` info { flavourInfo = fl }
+setWorkerInfo info wk = wk `seq` info { workerInfo = wk }
+setSpecInfo info sp = PSEQ sp (info { specInfo = sp })
+setTyGenInfo info tg = tg `seq` info { tyGenInfo = tg }
+setInlinePragInfo info pr = pr `seq` info { inlinePragInfo = pr }
+setOccInfo info oc = oc `seq` info { occInfo = oc }
+setStrictnessInfo info st = st `seq` info { strictnessInfo = st }
+ -- Try to avoid spack leaks by seq'ing
+
+setUnfoldingInfo info uf
+ | isEvaldUnfolding uf && isStrict (demandInfo info)
+ -- If the unfolding is a value, the demand info may
+ -- go pear-shaped, so we nuke it. Example:
+ -- let x = (a,b) in
+ -- case x of (p,q) -> h p q x
+ -- Here x is certainly demanded. But after we've nuked
+ -- the case, we'll get just
+ -- let x = (a,b) in h a b x
+ -- and now x is not demanded (I'm assuming h is lazy)
+ -- This really happens. The solution here is a bit ad hoc...
+ = info { unfoldingInfo = uf, demandInfo = wwLazy }
+
+ | otherwise
+ -- We do *not* seq on the unfolding info, For some reason, doing so
+ -- actually increases residency significantly.
+ = info { unfoldingInfo = uf }
+
+setDemandInfo info dd = info { demandInfo = dd }
+setArityInfo info ar = info { arityInfo = ar }
+setCafInfo info cf = info { cafInfo = cf }
+setCprInfo info cp = info { cprInfo = cp }
+setLBVarInfo info lb = info { lbvarInfo = lb }
+
+setNoDiscardInfo info = case flavourInfo info of
+ VanillaId -> info { flavourInfo = ExportedId }
+ other -> info
+zapSpecPragInfo info = case flavourInfo info of
+ SpecPragmaId -> info { flavourInfo = VanillaId }
+ other -> info
\end{code}
\begin{code}
-noIdInfo = IdInfo {
- arityInfo = UnknownArity,
- demandInfo = wwLazy,
- specInfo = emptySpecEnv,
- strictnessInfo = NoStrictnessInfo,
- unfoldingInfo = noUnfolding,
- updateInfo = NoUpdateInfo,
- cafInfo = MayHaveCafRefs,
- inlinePragInfo = NoInlinePragInfo
+vanillaIdInfo :: IdInfo
+ -- Used for locally-defined Ids
+ -- We are going to calculate correct CAF information at the end
+vanillaIdInfo = mkIdInfo VanillaId NoCafRefs
+
+constantIdInfo :: IdInfo
+ -- Used for imported Ids
+ -- The default is that they *do* have CAFs; an interface-file pragma
+ -- may say "oh no it doesn't", but in the absence of such a pragma
+ -- we'd better assume it does
+constantIdInfo = mkIdInfo ConstantId MayHaveCafRefs
+
+mkIdInfo :: IdFlavour -> CafInfo -> IdInfo
+mkIdInfo flv caf
+ = IdInfo {
+ flavourInfo = flv,
+ cafInfo = caf,
+ arityInfo = UnknownArity,
+ demandInfo = wwLazy,
+ specInfo = emptyCoreRules,
+ tyGenInfo = noTyGenInfo,
+ workerInfo = NoWorker,
+ strictnessInfo = NoStrictnessInfo,
+ unfoldingInfo = noUnfolding,
+ cprInfo = NoCPRInfo,
+ lbvarInfo = NoLBVarInfo,
+ inlinePragInfo = NoInlinePragInfo,
+ occInfo = NoOccInfo
}
\end{code}
+
+%************************************************************************
+%* *
+\subsection{Flavour}
+%* *
+%************************************************************************
+
\begin{code}
-ppIdInfo :: IdInfo -> SDoc
-ppIdInfo (IdInfo {arityInfo,
- demandInfo,
- specInfo,
- strictnessInfo,
- unfoldingInfo,
- updateInfo,
- cafInfo,
- inlinePragInfo})
- = hsep [
- ppArityInfo arityInfo,
- ppUpdateInfo updateInfo,
- ppStrictnessInfo strictnessInfo,
- ppr demandInfo,
- ppCafInfo cafInfo
- -- Inline pragma printed out with all binders; see PprCore.pprIdBndr
- ]
+data IdFlavour
+ = VanillaId -- Locally defined, not exported
+ | ExportedId -- Locally defined, exported
+ | SpecPragmaId -- Locally defined, RHS holds specialised call
+
+ | ConstantId -- Imported from elsewhere, or a default method Id.
+
+ | DictFunId -- We flag dictionary functions so that we can
+ -- conveniently extract the DictFuns from a set of
+ -- bindings when building a module's interface
+
+ | DataConId DataCon -- The Id for a data constructor *worker*
+ | DataConWrapId DataCon -- The Id for a data constructor *wrapper*
+ -- [the only reasons we need to know is so that
+ -- a) we can suppress printing a definition in the interface file
+ -- b) when typechecking a pattern we can get from the
+ -- Id back to the data con]
+ | PrimOpId PrimOp -- The Id for a primitive operator
+ | RecordSelId FieldLabel -- The Id for a record selector
+
+
+makeConstantFlavour :: IdFlavour -> IdFlavour
+makeConstantFlavour flavour = new_flavour
+ where new_flavour = case flavour of
+ VanillaId -> ConstantId
+ ExportedId -> ConstantId
+ ConstantId -> ConstantId -- e.g. Default methods
+ DictFunId -> DictFunId
+ flavour -> pprTrace "makeConstantFlavour"
+ (ppFlavourInfo flavour)
+ flavour
+
+
+ppFlavourInfo :: IdFlavour -> SDoc
+ppFlavourInfo VanillaId = empty
+ppFlavourInfo ExportedId = ptext SLIT("[Exported]")
+ppFlavourInfo SpecPragmaId = ptext SLIT("[SpecPrag]")
+ppFlavourInfo ConstantId = ptext SLIT("[Constant]")
+ppFlavourInfo DictFunId = ptext SLIT("[DictFun]")
+ppFlavourInfo (DataConId _) = ptext SLIT("[DataCon]")
+ppFlavourInfo (DataConWrapId _) = ptext SLIT("[DataConWrapper]")
+ppFlavourInfo (PrimOpId _) = ptext SLIT("[PrimOp]")
+ppFlavourInfo (RecordSelId _) = ptext SLIT("[RecSel]")
+
+seqFlavour :: IdFlavour -> ()
+seqFlavour f = f `seq` ()
\end{code}
+The @SpecPragmaId@ exists only to make Ids that are
+on the *LHS* of bindings created by SPECIALISE pragmas;
+eg: s = f Int d
+The SpecPragmaId is never itself mentioned; it
+exists solely so that the specialiser will find
+the call to f, and make specialised version of it.
+The SpecPragmaId binding is discarded by the specialiser
+when it gathers up overloaded calls.
+Meanwhile, it is not discarded as dead code.
+
+
%************************************************************************
%* *
\subsection[arity-IdInfo]{Arity info about an @Id@}
\begin{code}
data ArityInfo
= UnknownArity -- No idea
- | ArityExactly Int -- Arity is exactly this
- | ArityAtLeast Int -- Arity is this or greater
+
+ | ArityExactly Arity -- Arity is exactly this. We use this when importing a
+ -- function; it's already been compiled and we know its
+ -- arity for sure.
+
+ | ArityAtLeast Arity -- A partial application of this Id to up to n-1 value arguments
+ -- does essentially no work. That is not necessarily the
+ -- same as saying that it has n leading lambdas, because coerces
+ -- may get in the way.
+
+ -- functions in the module being compiled. Their arity
+ -- might increase later in the compilation process, if
+ -- an extra lambda floats up to the binding site.
+ deriving( Eq )
+
+seqArity :: ArityInfo -> ()
+seqArity a = arityLowerBound a `seq` ()
exactArity = ArityExactly
atLeastArity = ArityAtLeast
unknownArity = UnknownArity
-arityLowerBound :: ArityInfo -> Int
+arityLowerBound :: ArityInfo -> Arity
arityLowerBound UnknownArity = 0
arityLowerBound (ArityAtLeast n) = n
arityLowerBound (ArityExactly n) = n
+hasArity :: ArityInfo -> Bool
+hasArity UnknownArity = False
+hasArity other = True
ppArityInfo UnknownArity = empty
ppArityInfo (ArityExactly arity) = hsep [ptext SLIT("__A"), int arity]
\begin{code}
data InlinePragInfo
= NoInlinePragInfo
+ | IMustNotBeINLINEd Bool -- True <=> came from an INLINE prag, False <=> came from a NOINLINE prag
+ (Maybe Int) -- Phase number from pragma, if any
+ deriving( Eq )
+ -- The True, Nothing case doesn't need to be recorded
- | IAmASpecPragmaId -- Used for spec-pragma Ids; don't discard or inline
-
- | IWantToBeINLINEd -- User INLINE pragma
- | IMustNotBeINLINEd -- User NOINLINE pragma
+ -- SEE COMMENTS WITH CoreUnfold.blackListed on the
+ -- exact significance of the IMustNotBeINLINEd pragma
- | IAmALoopBreaker -- Used by the occurrence analyser to mark loop-breakers
- -- in a group of recursive definitions
+isNeverInlinePrag :: InlinePragInfo -> Bool
+isNeverInlinePrag (IMustNotBeINLINEd _ Nothing) = True
+isNeverInlinePrag other = False
- | ICanSafelyBeINLINEd -- Used by the occurrence analyser to mark things
- -- that manifesly occur once, not inside SCCs,
- -- not in constructor arguments
+neverInlinePrag :: InlinePragInfo
+neverInlinePrag = IMustNotBeINLINEd True{-should be False? --SDM -} Nothing
- OccInfo -- Says whether the occurrence is inside a lambda
- -- If so, must only substitute WHNFs
+instance Outputable InlinePragInfo where
+ -- This is now parsed in interface files
+ ppr NoInlinePragInfo = empty
+ ppr other_prag = ptext SLIT("__U") <> pprInlinePragInfo other_prag
+
+pprInlinePragInfo NoInlinePragInfo = empty
+pprInlinePragInfo (IMustNotBeINLINEd True Nothing) = empty
+pprInlinePragInfo (IMustNotBeINLINEd True (Just n)) = brackets (int n)
+pprInlinePragInfo (IMustNotBeINLINEd False Nothing) = brackets (char '!')
+pprInlinePragInfo (IMustNotBeINLINEd False (Just n)) = brackets (char '!' <> int n)
+
+instance Show InlinePragInfo where
+ showsPrec p prag = showsPrecSDoc p (ppr prag)
+\end{code}
- Bool -- False <=> occurs in more than one case branch
- -- If so, there's a code-duplication issue
- | IAmDead -- Marks unused variables. Sometimes useful for
- -- lambda and case-bound variables.
+%************************************************************************
+%* *
+\subsection[TyGen-IdInfo]{Type generalisation info about an @Id@}
+%* *
+%************************************************************************
- | IMustBeINLINEd -- Absolutely must inline; used for PrimOps and
- -- constructors only.
+Certain passes (notably usage inference) may change the type of an
+identifier, modifying all in-scope uses of that identifier
+appropriately to maintain type safety.
-instance Outputable InlinePragInfo where
- ppr NoInlinePragInfo = empty
- ppr IMustBeINLINEd = ptext SLIT("__UU")
- ppr IWantToBeINLINEd = ptext SLIT("__U")
- ppr IMustNotBeINLINEd = ptext SLIT("__Unot")
- ppr IAmALoopBreaker = ptext SLIT("__Ux")
- ppr IAmDead = ptext SLIT("__Ud")
- ppr (ICanSafelyBeINLINEd _ _) = ptext SLIT("__Us")
- ppr IAmASpecPragmaId = ptext SLIT("__US")
+However, some identifiers must not have their types changed in this
+way, because their types are conjured up in the front end of the
+compiler rather than being read from the interface file. Default
+methods, dictionary functions, record selectors, and others are in
+this category. (see comment at TcClassDcl.tcClassSig).
-instance Show InlinePragInfo where
- showsPrec p prag = showsPrecSDoc p (ppr prag)
-\end{code}
+To indicate this property, such identifiers are marked TyGenNever.
-The @IMustNotBeDiscarded@ exists only to make Ids that are
-on the *LHS* of bindings created by SPECIALISE pragmas;
-eg: s = f Int d
-The SpecPragmaId is never itself mentioned; it
-exists solely so that the specialiser will find
-the call to f, and make specialised version of it.
-The SpecPragmaId binding is discarded by the specialiser
-when it gathers up overloaded calls.
-Meanwhile, it is not discarded as dead code.
+Furthermore, if the usage inference generates a usage-specialised
+variant of a function, we must NOT re-infer a fully-generalised type
+at the next inference. This finer property is indicated by a
+TyGenUInfo on the identifier.
\begin{code}
-data OccInfo
- = StrictOcc -- Occurs syntactically strictly;
- -- i.e. in a function position or case scrutinee
+data TyGenInfo
+ = NoTyGenInfo -- no restriction on type generalisation
- | LazyOcc -- Not syntactically strict (*even* that of a strict function)
- -- or in a case branch where there's more than one alternative
+ | TyGenUInfo [Maybe Type] -- restrict generalisation of this Id to
+ -- preserve specified usage annotations
- | InsideLam -- Inside a non-linear lambda (that is, a lambda which
- -- is sure to be instantiated only once).
- -- Substituting a redex for this occurrence is
- -- dangerous because it might duplicate work.
+ | TyGenNever -- never generalise the type of this Id
-instance Outputable OccInfo where
- ppr StrictOcc = text "s"
- ppr LazyOcc = empty
- ppr InsideLam = text "l"
+ deriving ( Eq )
+\end{code}
+For TyGenUInfo, the list has one entry for each usage annotation on
+the type of the Id, in left-to-right pre-order (annotations come
+before the type they annotate). Nothing means no restriction; Just
+usOnce or Just usMany forces that annotation to that value. Other
+usage annotations are illegal.
-notInsideLambda :: OccInfo -> Bool
-notInsideLambda StrictOcc = True
-notInsideLambda LazyOcc = True
-notInsideLambda InsideLam = False
+\begin{code}
+seqTyGenInfo :: TyGenInfo -> ()
+seqTyGenInfo NoTyGenInfo = ()
+seqTyGenInfo (TyGenUInfo us) = seqList us ()
+seqTyGenInfo TyGenNever = ()
+
+noTyGenInfo :: TyGenInfo
+noTyGenInfo = NoTyGenInfo
+
+isNoTyGenInfo :: TyGenInfo -> Bool
+isNoTyGenInfo NoTyGenInfo = True
+isNoTyGenInfo _ = False
+
+-- NB: There's probably no need to write this information out to the interface file.
+-- Why? Simply because imported identifiers never get their types re-inferred.
+-- But it's definitely nice to see in dumps, it for debugging purposes.
+
+ppTyGenInfo :: TyGenInfo -> SDoc
+ppTyGenInfo NoTyGenInfo = empty
+ppTyGenInfo (TyGenUInfo us) = ptext SLIT("__G") <+> text (tyGenInfoString us)
+ppTyGenInfo TyGenNever = ptext SLIT("__G N")
+
+tyGenInfoString us = map go us
+ where go Nothing = 'x' -- for legibility, choose
+ go (Just u) | u == usOnce = '1' -- chars with identity
+ | u == usMany = 'M' -- Z-encoding.
+ go other = pprPanic "IdInfo.tyGenInfoString: unexpected annotation" (ppr other)
+
+instance Outputable TyGenInfo where
+ ppr = ppTyGenInfo
+
+instance Show TyGenInfo where
+ showsPrec p c = showsPrecSDoc p (ppr c)
\end{code}
+
%************************************************************************
%* *
-\subsection[specialisation-IdInfo]{Specialisation info about an @Id@}
+\subsection[worker-IdInfo]{Worker info about an @Id@}
%* *
%************************************************************************
-A @IdSpecEnv@ holds details of an @Id@'s specialisations.
+If this Id has a worker then we store a reference to it. Worker
+functions are generated by the worker/wrapper pass. This uses
+information from the strictness and CPR analyses.
+
+There might not be a worker, even for a strict function, because:
+(a) the function might be small enough to inline, so no need
+ for w/w split
+(b) the strictness info might be "SSS" or something, so no w/w split.
\begin{code}
-type IdSpecEnv = SpecEnv CoreExpr
-\end{code}
-For example, if \tr{f}'s @SpecEnv@ contains the mapping:
-\begin{verbatim}
- [List a, b] ===> (\d -> f' a b)
-\end{verbatim}
-then when we find an application of f to matching types, we simply replace
-it by the matching RHS:
-\begin{verbatim}
- f (List Int) Bool ===> (\d -> f' Int Bool)
-\end{verbatim}
-All the stuff about how many dictionaries to discard, and what types
-to apply the specialised function to, are handled by the fact that the
-SpecEnv contains a template for the result of the specialisation.
+data WorkerInfo = NoWorker
+ | HasWorker Id Arity
+ -- The Arity is the arity of the *wrapper* at the moment of the
+ -- w/w split. See comments in MkIface.ifaceId, with the 'Worker' code.
-There is one more exciting case, which is dealt with in exactly the same
-way. If the specialised value is unboxed then it is lifted at its
-definition site and unlifted at its uses. For example:
+seqWorker :: WorkerInfo -> ()
+seqWorker (HasWorker id _) = id `seq` ()
+seqWorker NoWorker = ()
- pi :: forall a. Num a => a
+ppWorkerInfo NoWorker = empty
+ppWorkerInfo (HasWorker wk_id _) = ptext SLIT("__P") <+> ppr wk_id
-might have a specialisation
+noWorkerInfo = NoWorker
- [Int#] ===> (case pi' of Lift pi# -> pi#)
+workerExists :: WorkerInfo -> Bool
+workerExists NoWorker = False
+workerExists (HasWorker _ _) = True
-where pi' :: Lift Int# is the specialised version of pi.
+workerId :: WorkerInfo -> Id
+workerId (HasWorker id _) = id
+wrapperArity :: WorkerInfo -> Arity
+wrapperArity (HasWorker _ a) = a
+\end{code}
%************************************************************************
%* *
-\subsection[strictness-IdInfo]{Strictness info about an @Id@}
+\subsection[CAF-IdInfo]{CAF-related information}
%* *
%************************************************************************
-We specify the strictness of a function by giving information about
-each of the ``wrapper's'' arguments (see the description about
-worker/wrapper-style transformations in the PJ/Launchbury paper on
-unboxed types).
-
-The list of @Demands@ specifies: (a)~the strictness properties
-of a function's arguments; (b)~the {\em existence} of a ``worker''
-version of the function; and (c)~the type signature of that worker (if
-it exists); i.e. its calling convention.
-
-\begin{code}
-data StrictnessInfo
- = NoStrictnessInfo
-
- | BottomGuaranteed -- This Id guarantees never to return;
- -- it is bottom regardless of its arguments.
- -- Useful for "error" and other disguised
- -- variants thereof.
-
- | StrictnessInfo [Demand]
- Bool -- True <=> there is a worker. There might not be, even for a
- -- strict function, because:
- -- (a) the function might be small enough to inline,
- -- so no need for w/w split
- -- (b) the strictness info might be "SSS" or something, so no w/w split.
-
- -- Worker's Id, if applicable, and a list of the constructors
- -- mentioned by the wrapper. This is necessary so that the
- -- renamer can slurp them in. Without this info, the renamer doesn't
- -- know which data types to slurp in concretely. Remember, for
- -- strict things we don't put the unfolding in the interface file, to save space.
- -- This constructor list allows the renamer to behave much as if the
- -- unfolding *was* in the interface file.
-\end{code}
+This information is used to build Static Reference Tables (see
+simplStg/ComputeSRT.lhs).
\begin{code}
-mkStrictnessInfo :: [Demand] -> Bool -> StrictnessInfo
-
-mkStrictnessInfo xs has_wrkr
- | all isLazy xs = NoStrictnessInfo -- Uninteresting
- | otherwise = StrictnessInfo xs has_wrkr
+data CafInfo
+ = MayHaveCafRefs -- either:
+ -- (1) A function or static constructor
+ -- that refers to one or more CAFs,
+ -- (2) A real live CAF
-noStrictnessInfo = NoStrictnessInfo
-mkBottomStrictnessInfo = BottomGuaranteed
+ | NoCafRefs -- A function or static constructor
+ -- that refers to no CAFs.
-bottomIsGuaranteed BottomGuaranteed = True
-bottomIsGuaranteed other = False
+-- LATER: not sure how easy this is...
+-- | OneCafRef Id
-ppStrictnessInfo NoStrictnessInfo = empty
-ppStrictnessInfo BottomGuaranteed = ptext SLIT("__bot")
-ppStrictnessInfo (StrictnessInfo wrapper_args wrkr_maybe)
- = hsep [ptext SLIT("__S"), pprDemands wrapper_args]
-\end{code}
+mayHaveCafRefs MayHaveCafRefs = True
+mayHaveCafRefs _ = False
+seqCaf c = c `seq` ()
-\begin{code}
-workerExists :: StrictnessInfo -> Bool
-workerExists (StrictnessInfo _ worker_exists) = worker_exists
-workerExists other = False
+ppCafInfo NoCafRefs = ptext SLIT("__C")
+ppCafInfo MayHaveCafRefs = empty
\end{code}
%************************************************************************
%* *
-\subsection[update-IdInfo]{Update-analysis info about an @Id@}
+\subsection[cpr-IdInfo]{Constructed Product Result info about an @Id@}
%* *
%************************************************************************
+If the @Id@ is a function then it may have CPR info. A CPR analysis
+phase detects whether:
+
+\begin{enumerate}
+\item
+The function's return value has a product type, i.e. an algebraic type
+with a single constructor. Examples of such types are tuples and boxed
+primitive values.
+\item
+The function always 'constructs' the value that it is returning. It
+must do this on every path through, and it's OK if it calls another
+function which constructs the result.
+\end{enumerate}
+
+If this is the case then we store a template which tells us the
+function has the CPR property and which components of the result are
+also CPRs.
+
\begin{code}
-data UpdateInfo
- = NoUpdateInfo
- | SomeUpdateInfo UpdateSpec
- deriving (Eq, Ord)
- -- we need Eq/Ord to cross-chk update infos in interfaces
-
--- the form in which we pass update-analysis info between modules:
-type UpdateSpec = [Int]
+data CprInfo
+ = NoCPRInfo
+ | ReturnsCPR -- Yes, this function returns a constructed product
+ -- Implicitly, this means "after the function has been applied
+ -- to all its arguments", so the worker/wrapper builder in
+ -- WwLib.mkWWcpr checks that that it is indeed saturated before
+ -- making use of the CPR info
+
+ -- We used to keep nested info about sub-components, but
+ -- we never used it so I threw it away
\end{code}
\begin{code}
-mkUpdateInfo = SomeUpdateInfo
+seqCpr :: CprInfo -> ()
+seqCpr ReturnsCPR = ()
+seqCpr NoCPRInfo = ()
+
+noCprInfo = NoCPRInfo
-updateInfoMaybe NoUpdateInfo = Nothing
-updateInfoMaybe (SomeUpdateInfo []) = Nothing
-updateInfoMaybe (SomeUpdateInfo u) = Just u
+ppCprInfo NoCPRInfo = empty
+ppCprInfo ReturnsCPR = ptext SLIT("__M")
+
+instance Outputable CprInfo where
+ ppr = ppCprInfo
+
+instance Show CprInfo where
+ showsPrec p c = showsPrecSDoc p (ppr c)
\end{code}
-Text instance so that the update annotations can be read in.
+
+%************************************************************************
+%* *
+\subsection[lbvar-IdInfo]{Lambda-bound var info about an @Id@}
+%* *
+%************************************************************************
+
+If the @Id@ is a lambda-bound variable then it may have lambda-bound
+var info. The usage analysis (UsageSP) detects whether the lambda
+binding this var is a ``one-shot'' lambda; that is, whether it is
+applied at most once.
+
+This information may be useful in optimisation, as computations may
+safely be floated inside such a lambda without risk of duplicating
+work.
+
+\begin{code}
+data LBVarInfo
+ = NoLBVarInfo
+
+ | LBVarInfo Type -- The lambda that binds this Id has this usage
+ -- annotation (i.e., if ==usOnce, then the
+ -- lambda is applied at most once).
+ -- The annotation's kind must be `$'
+ -- HACK ALERT! placing this info here is a short-term hack,
+ -- but it minimises changes to the rest of the compiler.
+ -- Hack agreed by SLPJ/KSW 1999-04.
+
+seqLBVar l = l `seq` ()
+\end{code}
\begin{code}
-ppUpdateInfo NoUpdateInfo = empty
-ppUpdateInfo (SomeUpdateInfo []) = empty
-ppUpdateInfo (SomeUpdateInfo spec) = (<>) (ptext SLIT("__U ")) (hcat (map int spec))
+hasNoLBVarInfo NoLBVarInfo = True
+hasNoLBVarInfo other = False
+
+noLBVarInfo = NoLBVarInfo
+
+-- not safe to print or parse LBVarInfo because it is not really a
+-- property of the definition, but a property of the context.
+pprLBVarInfo NoLBVarInfo = empty
+pprLBVarInfo (LBVarInfo u) | u == usOnce
+ = getPprStyle $ \ sty ->
+ if ifaceStyle sty
+ then empty
+ else ptext SLIT("OneShot")
+ | otherwise
+ = empty
+
+instance Outputable LBVarInfo where
+ ppr = pprLBVarInfo
+
+instance Show LBVarInfo where
+ showsPrec p c = showsPrecSDoc p (ppr c)
\end{code}
+
%************************************************************************
%* *
-\subsection[CAF-IdInfo]{CAF-related information}
+\subsection{Bulk operations on IdInfo}
%* *
%************************************************************************
-This information is used to build Static Reference Tables (see
-simplStg/ComputeSRT.lhs).
+@zapLamInfo@ is used for lambda binders that turn out to to be
+part of an unsaturated lambda
\begin{code}
-data CafInfo
- = MayHaveCafRefs -- either:
- -- (1) A function or static constructor
- -- that refers to one or more CAFs,
- -- (2) A real live CAF
+zapLamInfo :: IdInfo -> Maybe IdInfo
+zapLamInfo info@(IdInfo {occInfo = occ, demandInfo = demand})
+ | is_safe_occ && not (isStrict demand)
+ = Nothing
+ | otherwise
+ = Just (info {occInfo = safe_occ,
+ demandInfo = wwLazy})
+ where
+ -- The "unsafe" occ info is the ones that say I'm not in a lambda
+ -- because that might not be true for an unsaturated lambda
+ is_safe_occ = case occ of
+ OneOcc in_lam once -> in_lam
+ other -> True
+
+ safe_occ = case occ of
+ OneOcc _ once -> OneOcc insideLam once
+ other -> occ
+\end{code}
- | NoCafRefs -- A function or static constructor
- -- that refers to no CAFs.
+\begin{code}
+zapDemandInfo :: IdInfo -> Maybe IdInfo
+zapDemandInfo info@(IdInfo {demandInfo = demand})
+ | not (isStrict demand) = Nothing
+ | otherwise = Just (info {demandInfo = wwLazy})
+\end{code}
--- LATER: not sure how easy this is...
--- | OneCafRef Id
+copyIdInfo is used when shorting out a top-level binding
+ f_local = BIG
+ f = f_local
+where f is exported. We are going to swizzle it around to
+ f = BIG
+ f_local = f
+
+BUT (a) we must be careful about messing up rules
+ (b) we must ensure f's IdInfo ends up right
+
+(a) Messing up the rules
+~~~~~~~~~~~~~~~~~~~~
+The example that went bad on me was this one:
+
+ iterate :: (a -> a) -> a -> [a]
+ iterate = iterateList
+
+ iterateFB c f x = x `c` iterateFB c f (f x)
+ iterateList f x = x : iterateList f (f x)
+
+ {-# RULES
+ "iterate" forall f x. iterate f x = build (\c _n -> iterateFB c f x)
+ "iterateFB" iterateFB (:) = iterateList
+ #-}
+
+This got shorted out to:
+
+ iterateList :: (a -> a) -> a -> [a]
+ iterateList = iterate
+
+ iterateFB c f x = x `c` iterateFB c f (f x)
+ iterate f x = x : iterate f (f x)
+
+ {-# RULES
+ "iterate" forall f x. iterate f x = build (\c _n -> iterateFB c f x)
+ "iterateFB" iterateFB (:) = iterate
+ #-}
+
+And now we get an infinite loop in the rule system
+ iterate f x -> build (\cn -> iterateFB c f x
+ -> iterateFB (:) f x
+ -> iterate f x
+
+Tiresome solution: don't do shorting out if f has rewrite rules.
+Hence shortableIdInfo.
+
+(b) Keeping the IdInfo right
+~~~~~~~~~~~~~~~~~~~~~~~~
+We want to move strictness/worker info from f_local to f, but keep the rest.
+Hence copyIdInfo.
-ppCafInfo NoCafRefs = ptext SLIT("__C")
-ppCafInfo MayHaveCafRefs = empty
+\begin{code}
+shortableIdInfo :: IdInfo -> Bool
+shortableIdInfo info = isEmptyCoreRules (specInfo info)
+
+copyIdInfo :: IdInfo -- f_local
+ -> IdInfo -- f (the exported one)
+ -> IdInfo -- New info for f
+copyIdInfo f_local f = f { strictnessInfo = strictnessInfo f_local,
+ workerInfo = workerInfo f_local,
+ cprInfo = cprInfo f_local
+ }
\end{code}