{- (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 FlexibleContexts #-} {-# LANGUAGE BinaryLiterals #-} {-# OPTIONS_GHC -Wno-incomplete-record-updates #-} module GHC.Types.Id.Info ( -- * 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, trimUnfolding, -- ** The ArityInfo type ArityInfo, unknownArity, arityInfo, setArityInfo, ppArityInfo, callArityInfo, setCallArityInfo, -- ** Demand and strictness Info dmdSigInfo, setDmdSigInfo, cprSigInfo, setCprSigInfo, demandInfo, setDemandInfo, pprStrictness, -- ** Unfolding Info realUnfoldingInfo, unfoldingInfo, setUnfoldingInfo, hasInlineUnfolding, -- ** The InlinePragInfo type InlinePragInfo, inlinePragInfo, setInlinePragInfo, -- ** The OccInfo type OccInfo(..), isDeadOcc, isStrongLoopBreaker, isWeakLoopBreaker, occInfo, setOccInfo, InsideLam(..), BranchCount, TailCallInfo(..), tailCallInfo, isAlwaysTailCalled, -- ** The RuleInfo type RuleInfo(..), emptyRuleInfo, isEmptyRuleInfo, ruleInfoFreeVars, ruleInfoRules, setRuleInfoHead, ruleInfo, setRuleInfo, tagSigInfo, -- ** The CAFInfo type CafInfo(..), ppCafInfo, mayHaveCafRefs, cafInfo, setCafInfo, -- ** The LambdaFormInfo type LambdaFormInfo, lfInfo, setLFInfo, setTagSig, tagSig, -- ** Tick-box Info TickBoxOp(..), TickBoxId, -- ** Levity info LevityInfo, levityInfo, setNeverRepPoly, setLevityInfoWithType, isNeverRepPolyIdInfo ) where import GHC.Prelude import GHC.Core import GHC.Core.Class import {-# SOURCE #-} GHC.Builtin.PrimOps (PrimOp) import GHC.Types.Name import GHC.Types.Var.Set import GHC.Types.Basic import GHC.Core.DataCon import GHC.Core.TyCon import GHC.Core.PatSyn import GHC.Core.Type import GHC.Types.ForeignCall import GHC.Unit.Module import GHC.Types.Demand import GHC.Types.Cpr import GHC.Utils.Misc import GHC.Utils.Outputable import GHC.Utils.Panic import GHC.Utils.Panic.Plain import GHC.Stg.InferTags.TagSig import Data.Word import GHC.StgToCmm.Types (LambdaFormInfo) -- infixl so you can say (id `set` a `set` b) infixl 1 `setRuleInfo`, `setArityInfo`, `setInlinePragInfo`, `setUnfoldingInfo`, `setOneShotInfo`, `setOccInfo`, `setCafInfo`, `setDmdSigInfo`, `setCprSigInfo`, `setDemandInfo`, `setNeverRepPoly`, `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 GHC.Tc.TyCl | 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 (Maybe [CbvMark]) -- ^ An 'Id' for a join point taking n arguments -- Note [Join points] in "GHC.Core" -- Can also work as a WorkerLikeId if given `CbvMark`s. -- See Note [CBV Function Ids] -- The [CbvMark] is always empty (and ignored) until after Tidy. | WorkerLikeId [CbvMark] -- ^ An 'Id' for a worker like function, which might expect some arguments to be -- passed both evaluated and tagged. -- Worker like functions are create by W/W and SpecConstr and we can expect that they -- aren't used unapplied. -- See Note [CBV Function Ids] -- See Note [Tag Inference] -- The [CbvMark] is always empty (and ignored) until after Tidy for ids from the current -- module. {- Note [CBV Function Ids] ~~~~~~~~~~~~~~~~~~~~~~~~~~~ A WorkerLikeId essentially allows us to constrain the calling convention for the given Id. Each such Id carries with it a list of CbvMarks with each element representing a value argument. Arguments who have a matching `MarkedCbv` entry in the list need to be passed evaluated+*properly tagged*. CallByValueFunIds give us additional expressiveness which we use to improve runtime. This is all part of the TagInference work. See also Note [Tag Inference]. They allows us to express the fact that an argument is not only evaluated to WHNF once we entered it's RHS but also that an lifted argument is already *properly tagged* once we jump into the RHS. This means when e.g. branching on such an argument the RHS doesn't needed to perform an eval check to ensure the argument isn't an indirection. All seqs on such an argument in the functions body become no-ops as well. The invariants around the arguments of call by value function like Ids are then: * In any call `(f e1 .. en)`, if `f`'s i'th argument is marked `MarkedCbv`, then the caller must ensure that the i'th argument * points directly to the value (and hence is certainly evaluated before the call) * is a properly tagged pointer to that value * The following functions (and only these functions) have `CbvMarks`: * Any `WorkerLikeId` * Some `JoinId` bindings. This works analogous to the Strict Field Invariant. See also Note [Strict Field Invariant]. To make this work what we do is: * During W/W and SpecConstr any worker/specialized binding we introduce is marked as a worker binding by `asWorkerLikeId`. * W/W and SpecConstr further set OtherCon[] unfoldings on arguments which represent contents of a strict fields. * During Tidy we look at all bindings. For any callByValueLike Id and join point we mark arguments as cbv if they Are strict. We don't do so for regular bindings. See Note [Use CBV semantics only for join points and workers] for why. We might have made some ids rhs *more* strict in order to make their arguments be passed CBV. See Note [Call-by-value for worker args] for why. * During CorePrep calls to CallByValueFunIds are eta expanded. * During Stg CodeGen: * When we see a call to a callByValueLike Id: * We check if all arguments marked to be passed unlifted are already tagged. * If they aren't we will wrap the call in case expressions which will evaluate+tag these arguments before jumping to the function. * During Cmm codeGen: * When generating code for the RHS of a StrictWorker binding we omit tag checks when using arguments marked as tagged. We only use this for workers and specialized versions of SpecConstr But we also check other functions during tidy and potentially turn some of them into call by value functions and mark some of their arguments as call-by-value by looking at argument unfoldings. NB: I choose to put the information into a new Id constructor since these are loaded at all optimization levels. This makes it trivial to ensure the additional calling convention demands are available at all call sites. Putting it into IdInfo would require us at the very least to always decode the IdInfo just to decide if we need to throw it away or not after. Note [Use CBV semantics only for join points and workers] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A function with cbv-semantics requires arguments to be visible and if no arguments are visible requires us to eta-expand it's call site. That is for a binding with three cbv arguments like `w[WorkerLikeId[!,!,!]]` we would need to eta expand undersaturated occurences like `map w xs` into `map (\x1 x2 x3 -> w x1 x2 x3) xs. In experiments it turned out that the code size increase of doing so can outweigh the performance benefits of doing so. So we only do this for join points, workers and specialized functions (from SpecConstr). Join points are naturally always called saturated so this problem can't occur for them. For workers and specialized functions there are also always at least some applied arguments as we won't inline the wrapper/apply their rule if there are unapplied occurances like `map f xs`. -} -- | 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, (Maybe [CbvMark])) isJoinIdDetails_maybe (JoinId join_arity marks) = Just (join_arity, marks) 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 (WorkerLikeId dmds) = text "StrictWorker" <> parens (ppr dmds) 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 marks) = text "JoinId" <> parens (int arity) <> parens (ppr marks) {- ************************************************************************ * * \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 { ruleInfo :: RuleInfo, -- ^ Specialisations of the 'Id's function which exist. -- See Note [Specialisations and RULES in IdInfo] realUnfoldingInfo :: Unfolding, -- ^ The 'Id's unfolding inlinePragInfo :: InlinePragma, -- ^ Any inline pragma attached to the 'Id' occInfo :: OccInfo, -- ^ How the 'Id' occurs in the program dmdSigInfo :: DmdSig, -- ^ A strictness signature. Digests how a function uses its arguments -- if applied to at least 'arityInfo' arguments. cprSigInfo :: CprSig, -- ^ Information on whether the function will ultimately return a -- freshly allocated constructor. demandInfo :: Demand, -- ^ ID demand information bitfield :: {-# UNPACK #-} !BitField, -- ^ Bitfield packs CafInfo, OneShotInfo, arity info, LevityInfo, and -- call arity info in one 64-bit word. Packing these fields reduces size -- of `IdInfo` from 12 words to 7 words and reduces residency by almost -- 4% in some programs. See #17497 and associated MR. -- -- See documentation of the getters for what these packed fields mean. lfInfo :: !(Maybe LambdaFormInfo), -- See documentation of the getters for what these packed fields mean. tagSig :: !(Maybe TagSig) } -- | Encodes arities, OneShotInfo, CafInfo and LevityInfo. -- From least-significant to most-significant bits: -- -- - Bit 0 (1): OneShotInfo -- - Bit 1 (1): CafInfo -- - Bit 2 (1): LevityInfo -- - Bits 3-32(30): Call Arity info -- - Bits 33-62(30): Arity info -- newtype BitField = BitField Word64 emptyBitField :: BitField emptyBitField = BitField 0 bitfieldGetOneShotInfo :: BitField -> OneShotInfo bitfieldGetOneShotInfo (BitField bits) = if testBit bits 0 then OneShotLam else NoOneShotInfo bitfieldGetCafInfo :: BitField -> CafInfo bitfieldGetCafInfo (BitField bits) = if testBit bits 1 then NoCafRefs else MayHaveCafRefs bitfieldGetLevityInfo :: BitField -> LevityInfo bitfieldGetLevityInfo (BitField bits) = if testBit bits 2 then NeverLevityPolymorphic else NoLevityInfo bitfieldGetCallArityInfo :: BitField -> ArityInfo bitfieldGetCallArityInfo (BitField bits) = fromIntegral (bits `shiftR` 3) .&. ((1 `shiftL` 30) - 1) bitfieldGetArityInfo :: BitField -> ArityInfo bitfieldGetArityInfo (BitField bits) = fromIntegral (bits `shiftR` 33) bitfieldSetOneShotInfo :: OneShotInfo -> BitField -> BitField bitfieldSetOneShotInfo info (BitField bits) = case info of NoOneShotInfo -> BitField (clearBit bits 0) OneShotLam -> BitField (setBit bits 0) bitfieldSetCafInfo :: CafInfo -> BitField -> BitField bitfieldSetCafInfo info (BitField bits) = case info of MayHaveCafRefs -> BitField (clearBit bits 1) NoCafRefs -> BitField (setBit bits 1) bitfieldSetLevityInfo :: LevityInfo -> BitField -> BitField bitfieldSetLevityInfo info (BitField bits) = case info of NoLevityInfo -> BitField (clearBit bits 2) NeverLevityPolymorphic -> BitField (setBit bits 2) bitfieldSetCallArityInfo :: ArityInfo -> BitField -> BitField bitfieldSetCallArityInfo info bf@(BitField bits) = assert (info < 2^(30 :: Int) - 1) $ bitfieldSetArityInfo (bitfieldGetArityInfo bf) $ BitField ((fromIntegral info `shiftL` 3) .|. (bits .&. 0b111)) bitfieldSetArityInfo :: ArityInfo -> BitField -> BitField bitfieldSetArityInfo info (BitField bits) = assert (info < 2^(30 :: Int) - 1) $ BitField ((fromIntegral info `shiftL` 33) .|. (bits .&. ((1 `shiftL` 33) - 1))) -- Getters -- | When applied, will this Id ever have a representation-polymorphic type? levityInfo :: IdInfo -> LevityInfo levityInfo = bitfieldGetLevityInfo . bitfield -- | Info about a lambda-bound variable, if the 'Id' is one oneShotInfo :: IdInfo -> OneShotInfo oneShotInfo = bitfieldGetOneShotInfo . bitfield -- | 'Id' arity, as computed by "GHC.Core.Opt.Arity". Specifies how many arguments -- this 'Id' has to be applied to before it doesn any meaningful work. arityInfo :: IdInfo -> ArityInfo arityInfo = bitfieldGetArityInfo . bitfield -- | 'Id' CAF info cafInfo :: IdInfo -> CafInfo cafInfo = bitfieldGetCafInfo . bitfield -- | How this is called. This is the number of arguments to which a binding can -- be eta-expanded without losing any sharing. n <=> all calls have at least n -- arguments callArityInfo :: IdInfo -> ArityInfo callArityInfo = bitfieldGetCallArityInfo . bitfield tagSigInfo :: IdInfo -> Maybe TagSig tagSigInfo = tagSig -- 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 space leaks by seq'ing -- | Essentially returns the 'realUnfoldingInfo' field, but does not expose the -- unfolding of a strong loop breaker. -- -- This is the right thing to call if you plan to decide whether an unfolding -- will inline. unfoldingInfo :: IdInfo -> Unfolding unfoldingInfo info | isStrongLoopBreaker (occInfo info) = trimUnfolding $ realUnfoldingInfo info | otherwise = realUnfoldingInfo info 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 { realUnfoldingInfo = uf } hasInlineUnfolding :: IdInfo -> Bool -- ^ True of a /non-loop-breaker/ Id that has a /stable/ unfolding that is -- (a) always inlined; that is, with an `UnfWhen` guidance, or -- (b) a DFunUnfolding which never needs to be inlined hasInlineUnfolding info = isInlineUnfolding (unfoldingInfo info) setArityInfo :: IdInfo -> ArityInfo -> IdInfo setArityInfo info ar = info { bitfield = bitfieldSetArityInfo ar (bitfield info) } setCallArityInfo :: IdInfo -> ArityInfo -> IdInfo setCallArityInfo info ar = info { bitfield = bitfieldSetCallArityInfo ar (bitfield info) } setCafInfo :: IdInfo -> CafInfo -> IdInfo setCafInfo info caf = info { bitfield = bitfieldSetCafInfo caf (bitfield info) } setLFInfo :: IdInfo -> LambdaFormInfo -> IdInfo setLFInfo info lf = info { lfInfo = Just lf } setTagSig :: IdInfo -> TagSig -> IdInfo setTagSig info sig = info { tagSig = Just sig } setOneShotInfo :: IdInfo -> OneShotInfo -> IdInfo setOneShotInfo info lb = info { bitfield = bitfieldSetOneShotInfo lb (bitfield info) } setDemandInfo :: IdInfo -> Demand -> IdInfo setDemandInfo info dd = dd `seq` info { demandInfo = dd } setDmdSigInfo :: IdInfo -> DmdSig -> IdInfo setDmdSigInfo info dd = dd `seq` info { dmdSigInfo = dd } setCprSigInfo :: IdInfo -> CprSig -> IdInfo setCprSigInfo info cpr = cpr `seq` info { cprSigInfo = cpr } -- | Basic 'IdInfo' that carries no useful information whatsoever vanillaIdInfo :: IdInfo vanillaIdInfo = IdInfo { ruleInfo = emptyRuleInfo, realUnfoldingInfo = noUnfolding, inlinePragInfo = defaultInlinePragma, occInfo = noOccInfo, demandInfo = topDmd, dmdSigInfo = nopSig, cprSigInfo = topCprSig, bitfield = bitfieldSetCafInfo vanillaCafInfo $ bitfieldSetArityInfo unknownArity $ bitfieldSetCallArityInfo unknownArity $ bitfieldSetOneShotInfo NoOneShotInfo $ bitfieldSetLevityInfo NoLevityInfo $ emptyBitField, lfInfo = Nothing, tagSig = Nothing } -- | 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 GHC.Types.Id.Make. {- ************************************************************************ * * \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!) Note [Arity and function types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The arity of an 'Id' must never exceed the number of arguments that can be read off from the 'Id's type, possibly after expanding newtypes. Examples: f1 :: forall a. a -> a idArity f1 <= 1: only one value argument, of type 'a' f2 :: forall a. Show a => Int -> a idArity f2 <= 2: two value arguments, of types 'Show a' and 'Int'. newtype Id a = MkId a f3 :: forall b. Id (Int -> b) idArity f3 <= 1: there is one value argument, of type 'Int', hidden under the newtype. newtype RecFun = MkRecFun (Int -> RecFun) f4 :: RecFun no constraint on the arity of f4: we can unwrap as many layers of the newtype as we want, to get arbitrarily many arguments of type 'Int'. -} -- | 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. -- -- /Invariant:/ the 'Arity' of an 'Id' must never exceed the number of -- value arguments that appear in the type of the 'Id'. -- See Note [Arity and function types]. 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 :: DmdSig -> 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 just 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 GHC.Iface.Tidy, 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 "GHC.Core.Opt.OccurAnal" -- | Assume that no specializations 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 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 = NotInsideLam }) = False is_safe_occ _other = True safe_occ = case occ of OneOcc{} -> occ { occ_in_lam = IsInsideLam , occ_tail = NoTailCallInfo } IAmALoopBreaker{} -> occ { occ_tail = NoTailCallInfo } _other -> occ is_safe_dmd dmd = not (isStrUsedDmd 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 (dmdSigInfo info) = Just (info {dmdSigInfo = zapDmdEnvSig (dmdSigInfo info)}) | otherwise = Nothing zapUsedOnceInfo :: IdInfo -> Maybe IdInfo zapUsedOnceInfo info = Just $ info { dmdSigInfo = zapUsedOnceSig (dmdSigInfo info) , demandInfo = zapUsedOnceDemand (demandInfo info) } zapFragileInfo :: IdInfo -> Maybe IdInfo -- ^ Zap info that depends on free variables zapFragileInfo info@(IdInfo { occInfo = occ, realUnfoldingInfo = 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 -- ^ Zaps any core unfolding, but /preserves/ evaluated-ness, -- i.e. an unfolding of OtherCon zapFragileUnfolding unf -- N.B. isEvaldUnfolding catches *both* OtherCon [] *and* core unfoldings -- representing values. | isEvaldUnfolding unf = evaldUnfolding | otherwise = noUnfolding trimUnfolding :: Unfolding -> Unfolding -- Squash all unfolding info, preserving only evaluated-ness trimUnfolding unf | isEvaldUnfolding unf = evaldUnfolding | otherwise = noUnfolding 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 representation-polymorphic at any amount of saturation. This is helpful in optimizing representation polymorphism checks, allowing us to learn that something is not representation-polymorphic without actually figuring out its type. See exprHasFixedRuntimeRep in GHC.Core.Utils for where this info is used. Historical note: this was very important when representation polymorphism was checked in the desugarer (it was needed to prevent T5631 from blowing up). It's less important now that the checks happen in the typechecker, but remains useful. Refer to Note [The Concrete mechanism] in GHC.Tc.Utils.Concrete for details about the new approach being used. -} -- 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 representation-polymorphic -- (even when applied). The Type is only there for checking that it's really -- never representation-polymorphic. setNeverRepPoly :: HasDebugCallStack => IdInfo -> Type -> IdInfo setNeverRepPoly info ty = assertPpr (resultHasFixedRuntimeRep ty) (ppr ty) $ info { bitfield = bitfieldSetLevityInfo NeverLevityPolymorphic (bitfield info) } setLevityInfoWithType :: IdInfo -> Type -> IdInfo setLevityInfoWithType info ty | resultHasFixedRuntimeRep ty = info { bitfield = bitfieldSetLevityInfo NeverLevityPolymorphic (bitfield info) } | otherwise = info isNeverRepPolyIdInfo :: IdInfo -> Bool isNeverRepPolyIdInfo info | NeverLevityPolymorphic <- levityInfo info = True | otherwise = False