{- (c) The University of Glasgow 2006 (c) The GRASP/AQUA Project, Glasgow University, 1993-1998 \section[IdInfo]{@IdInfos@: Non-essential information about @Ids@} (And a pretty good illustration of quite a few things wrong with Haskell. [WDP 94/11]) -} {-# LANGUAGE CPP #-} {-# LANGUAGE FlexibleContexts #-} module IdInfo ( -- * The IdDetails type IdDetails(..), pprIdDetails, coVarDetails, isCoVarDetails, JoinArity, isJoinIdDetails_maybe, RecSelParent(..), -- * The IdInfo type IdInfo, -- Abstract vanillaIdInfo, noCafIdInfo, -- ** The OneShotInfo type OneShotInfo(..), oneShotInfo, noOneShotInfo, hasNoOneShotInfo, setOneShotInfo, -- ** Zapping various forms of Info zapLamInfo, zapFragileInfo, zapDemandInfo, zapUsageInfo, zapUsageEnvInfo, zapUsedOnceInfo, zapTailCallInfo, zapCallArityInfo, -- ** The ArityInfo type ArityInfo, unknownArity, arityInfo, setArityInfo, ppArityInfo, callArityInfo, setCallArityInfo, -- ** Demand and strictness Info strictnessInfo, setStrictnessInfo, demandInfo, setDemandInfo, pprStrictness, -- ** Unfolding Info unfoldingInfo, setUnfoldingInfo, -- ** The InlinePragInfo type InlinePragInfo, inlinePragInfo, setInlinePragInfo, -- ** The OccInfo type OccInfo(..), isDeadOcc, isStrongLoopBreaker, isWeakLoopBreaker, occInfo, setOccInfo, InsideLam, OneBranch, insideLam, notInsideLam, oneBranch, notOneBranch, TailCallInfo(..), tailCallInfo, isAlwaysTailCalled, -- ** The RuleInfo type RuleInfo(..), emptyRuleInfo, isEmptyRuleInfo, ruleInfoFreeVars, ruleInfoRules, setRuleInfoHead, ruleInfo, setRuleInfo, -- ** The CAFInfo type CafInfo(..), ppCafInfo, mayHaveCafRefs, cafInfo, setCafInfo, -- ** Tick-box Info TickBoxOp(..), TickBoxId, -- ** Levity info LevityInfo, levityInfo, setNeverLevPoly, setLevityInfoWithType, isNeverLevPolyIdInfo ) where #include "HsVersions.h" import CoreSyn import Class import {-# SOURCE #-} PrimOp (PrimOp) import Name import VarSet import BasicTypes import DataCon import TyCon import PatSyn import Type import ForeignCall import Outputable import Module import Demand import Util -- infixl so you can say (id `set` a `set` b) infixl 1 `setRuleInfo`, `setArityInfo`, `setInlinePragInfo`, `setUnfoldingInfo`, `setOneShotInfo`, `setOccInfo`, `setCafInfo`, `setStrictnessInfo`, `setDemandInfo`, `setNeverLevPoly`, `setLevityInfoWithType` {- ************************************************************************ * * IdDetails * * ************************************************************************ -} -- | Identifier Details -- -- The 'IdDetails' of an 'Id' give stable, and necessary, -- information about the Id. data IdDetails = VanillaId -- | The 'Id' for a record selector | RecSelId { sel_tycon :: RecSelParent , sel_naughty :: Bool -- True <=> a "naughty" selector which can't actually exist, for example @x@ in: -- data T = forall a. MkT { x :: a } } -- See Note [Naughty record selectors] in TcTyClsDecls | DataConWorkId DataCon -- ^ The 'Id' is for a data constructor /worker/ | DataConWrapId DataCon -- ^ The 'Id' is for a data constructor /wrapper/ -- [the only reasons we need to know is so that -- a) to support isImplicitId -- b) when desugaring a RecordCon we can get -- from the Id back to the data con] | ClassOpId Class -- ^ The 'Id' is a superclass selector, -- or class operation of a class | PrimOpId PrimOp -- ^ The 'Id' is for a primitive operator | FCallId ForeignCall -- ^ The 'Id' is for a foreign call. -- Type will be simple: no type families, newtypes, etc | TickBoxOpId TickBoxOp -- ^ The 'Id' is for a HPC tick box (both traditional and binary) | DFunId Bool -- ^ A dictionary function. -- Bool = True <=> the class has only one method, so may be -- implemented with a newtype, so it might be bad -- to be strict on this dictionary | CoVarId -- ^ A coercion variable -- This only covers /un-lifted/ coercions, of type -- (t1 ~# t2) or (t1 ~R# t2), not their lifted variants | JoinId JoinArity -- ^ An 'Id' for a join point taking n arguments -- Note [Join points] in CoreSyn -- | Recursive Selector Parent data RecSelParent = RecSelData TyCon | RecSelPatSyn PatSyn deriving Eq -- Either `TyCon` or `PatSyn` depending -- on the origin of the record selector. -- For a data type family, this is the -- /instance/ 'TyCon' not the family 'TyCon' instance Outputable RecSelParent where ppr p = case p of RecSelData ty_con -> ppr ty_con RecSelPatSyn ps -> ppr ps -- | Just a synonym for 'CoVarId'. Written separately so it can be -- exported in the hs-boot file. coVarDetails :: IdDetails coVarDetails = CoVarId -- | Check if an 'IdDetails' says 'CoVarId'. isCoVarDetails :: IdDetails -> Bool isCoVarDetails CoVarId = True isCoVarDetails _ = False isJoinIdDetails_maybe :: IdDetails -> Maybe JoinArity isJoinIdDetails_maybe (JoinId join_arity) = Just join_arity isJoinIdDetails_maybe _ = Nothing instance Outputable IdDetails where ppr = pprIdDetails pprIdDetails :: IdDetails -> SDoc pprIdDetails VanillaId = empty pprIdDetails other = brackets (pp other) where pp VanillaId = panic "pprIdDetails" pp (DataConWorkId _) = text "DataCon" pp (DataConWrapId _) = text "DataConWrapper" pp (ClassOpId {}) = text "ClassOp" pp (PrimOpId _) = text "PrimOp" pp (FCallId _) = text "ForeignCall" pp (TickBoxOpId _) = text "TickBoxOp" pp (DFunId nt) = text "DFunId" <> ppWhen nt (text "(nt)") pp (RecSelId { sel_naughty = is_naughty }) = brackets $ text "RecSel" <> ppWhen is_naughty (text "(naughty)") pp CoVarId = text "CoVarId" pp (JoinId arity) = text "JoinId" <> parens (int arity) {- ************************************************************************ * * \subsection{The main IdInfo type} * * ************************************************************************ -} -- | Identifier Information -- -- An 'IdInfo' gives /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. -- -- 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. -- -- Most of the 'IdInfo' gives information about the value, or definition, of -- the 'Id', independent of its usage. Exceptions to this -- are 'demandInfo', 'occInfo', 'oneShotInfo' and 'callArityInfo'. -- -- Performance note: when we update 'IdInfo', we have to reallocate this -- entire record, so it is a good idea not to let this data structure get -- too big. data IdInfo = IdInfo { arityInfo :: !ArityInfo, -- ^ 'Id' arity ruleInfo :: RuleInfo, -- ^ Specialisations of the 'Id's function which exist -- See Note [Specialisations and RULES in IdInfo] unfoldingInfo :: Unfolding, -- ^ The 'Id's unfolding cafInfo :: CafInfo, -- ^ 'Id' CAF info oneShotInfo :: OneShotInfo, -- ^ Info about a lambda-bound variable, if the 'Id' is one inlinePragInfo :: InlinePragma, -- ^ Any inline pragma atached to the 'Id' occInfo :: OccInfo, -- ^ How the 'Id' occurs in the program strictnessInfo :: StrictSig, -- ^ A strictness signature demandInfo :: Demand, -- ^ ID demand information callArityInfo :: !ArityInfo, -- ^ How this is called. -- n <=> all calls have at least n arguments levityInfo :: LevityInfo -- ^ when applied, will this Id ever have a levity-polymorphic type? } -- Setters setRuleInfo :: IdInfo -> RuleInfo -> IdInfo setRuleInfo info sp = sp `seq` info { ruleInfo = sp } setInlinePragInfo :: IdInfo -> InlinePragma -> IdInfo setInlinePragInfo info pr = pr `seq` info { inlinePragInfo = pr } setOccInfo :: IdInfo -> OccInfo -> IdInfo setOccInfo info oc = oc `seq` info { occInfo = oc } -- Try to avoid spack leaks by seq'ing setUnfoldingInfo :: IdInfo -> Unfolding -> IdInfo setUnfoldingInfo info uf = -- We don't seq the unfolding, as we generate intermediate -- unfoldings which are just thrown away, so evaluating them is a -- waste of time. -- seqUnfolding uf `seq` info { unfoldingInfo = uf } setArityInfo :: IdInfo -> ArityInfo -> IdInfo setArityInfo info ar = info { arityInfo = ar } setCallArityInfo :: IdInfo -> ArityInfo -> IdInfo setCallArityInfo info ar = info { callArityInfo = ar } setCafInfo :: IdInfo -> CafInfo -> IdInfo setCafInfo info caf = info { cafInfo = caf } setOneShotInfo :: IdInfo -> OneShotInfo -> IdInfo setOneShotInfo info lb = {-lb `seq`-} info { oneShotInfo = lb } setDemandInfo :: IdInfo -> Demand -> IdInfo setDemandInfo info dd = dd `seq` info { demandInfo = dd } setStrictnessInfo :: IdInfo -> StrictSig -> IdInfo setStrictnessInfo info dd = dd `seq` info { strictnessInfo = dd } -- | Basic 'IdInfo' that carries no useful information whatsoever vanillaIdInfo :: IdInfo vanillaIdInfo = IdInfo { cafInfo = vanillaCafInfo, arityInfo = unknownArity, ruleInfo = emptyRuleInfo, unfoldingInfo = noUnfolding, oneShotInfo = NoOneShotInfo, inlinePragInfo = defaultInlinePragma, occInfo = noOccInfo, demandInfo = topDmd, strictnessInfo = nopSig, callArityInfo = unknownArity, levityInfo = NoLevityInfo } -- | More informative 'IdInfo' we can use when we know the 'Id' has no CAF references noCafIdInfo :: IdInfo noCafIdInfo = vanillaIdInfo `setCafInfo` NoCafRefs -- Used for built-in type Ids in MkId. {- ************************************************************************ * * \subsection[arity-IdInfo]{Arity info about an @Id@} * * ************************************************************************ For locally-defined Ids, the code generator maintains its own notion of their arities; so it should not be asking... (but other things besides the code-generator need arity info!) -} -- | Arity Information -- -- An 'ArityInfo' of @n@ tells us that 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. -- -- The arity might increase later in the compilation process, if -- an extra lambda floats up to the binding site. type ArityInfo = Arity -- | It is always safe to assume that an 'Id' has an arity of 0 unknownArity :: Arity unknownArity = 0 ppArityInfo :: Int -> SDoc ppArityInfo 0 = empty ppArityInfo n = hsep [text "Arity", int n] {- ************************************************************************ * * \subsection{Inline-pragma information} * * ************************************************************************ -} -- | Inline Pragma Information -- -- Tells when the inlining is active. -- When it is active the thing may be inlined, depending on how -- big it is. -- -- If there was an @INLINE@ pragma, then as a separate matter, the -- RHS will have been made to look small with a Core inline 'Note' -- -- The default 'InlinePragInfo' is 'AlwaysActive', so the info serves -- entirely as a way to inhibit inlining until we want it type InlinePragInfo = InlinePragma {- ************************************************************************ * * Strictness * * ************************************************************************ -} pprStrictness :: StrictSig -> SDoc pprStrictness sig = ppr sig {- ************************************************************************ * * RuleInfo * * ************************************************************************ Note [Specialisations and RULES in IdInfo] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Generally speaking, a GlobalId has an *empty* RuleInfo. All their RULES are contained in the globally-built rule-base. In principle, one could attach the to M.f the RULES for M.f that are defined in M. But we don't do that for instance declarations and so we just treat them all uniformly. The EXCEPTION is PrimOpIds, which do have rules in their IdInfo. That is jsut for convenience really. However, LocalIds may have non-empty RuleInfo. We treat them differently because: a) they might be nested, in which case a global table won't work b) the RULE might mention free variables, which we use to keep things alive In TidyPgm, when the LocalId becomes a GlobalId, its RULES are stripped off and put in the global list. -} -- | Rule Information -- -- Records the specializations of this 'Id' that we know about -- in the form of rewrite 'CoreRule's that target them data RuleInfo = RuleInfo [CoreRule] DVarSet -- Locally-defined free vars of *both* LHS and RHS -- of rules. I don't think it needs to include the -- ru_fn though. -- Note [Rule dependency info] in OccurAnal -- | Assume that no specilizations exist: always safe emptyRuleInfo :: RuleInfo emptyRuleInfo = RuleInfo [] emptyDVarSet isEmptyRuleInfo :: RuleInfo -> Bool isEmptyRuleInfo (RuleInfo rs _) = null rs -- | Retrieve the locally-defined free variables of both the left and -- right hand sides of the specialization rules ruleInfoFreeVars :: RuleInfo -> DVarSet ruleInfoFreeVars (RuleInfo _ fvs) = fvs ruleInfoRules :: RuleInfo -> [CoreRule] ruleInfoRules (RuleInfo rules _) = rules -- | Change the name of the function the rule is keyed on on all of the 'CoreRule's setRuleInfoHead :: Name -> RuleInfo -> RuleInfo setRuleInfoHead fn (RuleInfo rules fvs) = RuleInfo (map (setRuleIdName fn) rules) fvs {- ************************************************************************ * * \subsection[CG-IdInfo]{Code generator-related information} * * ************************************************************************ -} -- CafInfo is used to build Static Reference Tables (see simplStg/SRT.hs). -- | Constant applicative form Information -- -- Records whether an 'Id' makes Constant Applicative Form references data CafInfo = MayHaveCafRefs -- ^ Indicates that the 'Id' is for either: -- -- 1. A function or static constructor -- that refers to one or more CAFs, or -- -- 2. A real live CAF | NoCafRefs -- ^ A function or static constructor -- that refers to no CAFs. deriving (Eq, Ord) -- | Assumes that the 'Id' has CAF references: definitely safe vanillaCafInfo :: CafInfo vanillaCafInfo = MayHaveCafRefs mayHaveCafRefs :: CafInfo -> Bool mayHaveCafRefs MayHaveCafRefs = True mayHaveCafRefs _ = False instance Outputable CafInfo where ppr = ppCafInfo ppCafInfo :: CafInfo -> SDoc ppCafInfo NoCafRefs = text "NoCafRefs" ppCafInfo MayHaveCafRefs = empty {- ************************************************************************ * * \subsection{Bulk operations on IdInfo} * * ************************************************************************ -} -- | This is used to remove information on lambda binders that we have -- setup as part of a lambda group, assuming they will be applied all at once, -- but turn out to be part of an unsaturated lambda as in e.g: -- -- > (\x1. \x2. e) arg1 zapLamInfo :: IdInfo -> Maybe IdInfo zapLamInfo info@(IdInfo {occInfo = occ, demandInfo = demand}) | is_safe_occ occ && is_safe_dmd demand = Nothing | otherwise = Just (info {occInfo = safe_occ, demandInfo = topDmd}) 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 occ | isAlwaysTailCalled occ = False is_safe_occ (OneOcc { occ_in_lam = in_lam }) = in_lam is_safe_occ _other = True safe_occ = case occ of OneOcc{} -> occ { occ_in_lam = True , occ_tail = NoTailCallInfo } IAmALoopBreaker{} -> occ { occ_tail = NoTailCallInfo } _other -> occ is_safe_dmd dmd = not (isStrictDmd dmd) -- | Remove all demand info on the 'IdInfo' zapDemandInfo :: IdInfo -> Maybe IdInfo zapDemandInfo info = Just (info {demandInfo = topDmd}) -- | Remove usage (but not strictness) info on the 'IdInfo' zapUsageInfo :: IdInfo -> Maybe IdInfo zapUsageInfo info = Just (info {demandInfo = zapUsageDemand (demandInfo info)}) -- | Remove usage environment info from the strictness signature on the 'IdInfo' zapUsageEnvInfo :: IdInfo -> Maybe IdInfo zapUsageEnvInfo info | hasDemandEnvSig (strictnessInfo info) = Just (info {strictnessInfo = zapUsageEnvSig (strictnessInfo info)}) | otherwise = Nothing zapUsedOnceInfo :: IdInfo -> Maybe IdInfo zapUsedOnceInfo info = Just $ info { strictnessInfo = zapUsedOnceSig (strictnessInfo info) , demandInfo = zapUsedOnceDemand (demandInfo info) } zapFragileInfo :: IdInfo -> Maybe IdInfo -- ^ Zap info that depends on free variables zapFragileInfo info@(IdInfo { occInfo = occ, unfoldingInfo = unf }) = new_unf `seq` -- The unfolding field is not (currently) strict, so we -- force it here to avoid a (zapFragileUnfolding unf) thunk -- which might leak space Just (info `setRuleInfo` emptyRuleInfo `setUnfoldingInfo` new_unf `setOccInfo` zapFragileOcc occ) where new_unf = zapFragileUnfolding unf zapFragileUnfolding :: Unfolding -> Unfolding zapFragileUnfolding unf | isFragileUnfolding unf = noUnfolding | otherwise = unf zapTailCallInfo :: IdInfo -> Maybe IdInfo zapTailCallInfo info = case occInfo info of occ | isAlwaysTailCalled occ -> Just (info `setOccInfo` safe_occ) | otherwise -> Nothing where safe_occ = occ { occ_tail = NoTailCallInfo } zapCallArityInfo :: IdInfo -> IdInfo zapCallArityInfo info = setCallArityInfo info 0 {- ************************************************************************ * * \subsection{TickBoxOp} * * ************************************************************************ -} type TickBoxId = Int -- | Tick box for Hpc-style coverage data TickBoxOp = TickBox Module {-# UNPACK #-} !TickBoxId instance Outputable TickBoxOp where ppr (TickBox mod n) = text "tick" <+> ppr (mod,n) {- ************************************************************************ * * Levity * * ************************************************************************ Note [Levity info] ~~~~~~~~~~~~~~~~~~ Ids store whether or not they can be levity-polymorphic at any amount of saturation. This is helpful in optimizing the levity-polymorphism check done in the desugarer, where we can usually learn that something is not levity-polymorphic without actually figuring out its type. See isExprLevPoly in CoreUtils for where this info is used. Storing this is required to prevent perf/compiler/T5631 from blowing up. -} -- See Note [Levity info] data LevityInfo = NoLevityInfo -- always safe | NeverLevityPolymorphic deriving Eq instance Outputable LevityInfo where ppr NoLevityInfo = text "NoLevityInfo" ppr NeverLevityPolymorphic = text "NeverLevityPolymorphic" -- | Marks an IdInfo describing an Id that is never levity polymorphic (even when -- applied). The Type is only there for checking that it's really never levity -- polymorphic setNeverLevPoly :: HasDebugCallStack => IdInfo -> Type -> IdInfo setNeverLevPoly info ty = ASSERT2( not (resultIsLevPoly ty), ppr ty ) info { levityInfo = NeverLevityPolymorphic } setLevityInfoWithType :: IdInfo -> Type -> IdInfo setLevityInfoWithType info ty | not (resultIsLevPoly ty) = info { levityInfo = NeverLevityPolymorphic } | otherwise = info isNeverLevPolyIdInfo :: IdInfo -> Bool isNeverLevPolyIdInfo info | NeverLevityPolymorphic <- levityInfo info = True | otherwise = False