2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
5 \section[Id]{@Ids@: Value and constructor identifiers}
10 -- GHC uses several kinds of name internally:
12 -- * 'OccName.OccName': see "OccName#name_types"
14 -- * 'RdrName.RdrName': see "RdrName#name_types"
16 -- * 'Name.Name': see "Name#name_types"
18 -- * 'Id.Id' represents names that not only have a 'Name.Name' but also a 'TypeRep.Type' and some additional
19 -- details (a 'IdInfo.IdInfo' and one of 'Var.LocalIdDetails' or 'IdInfo.GlobalIdDetails') that
20 -- are added, modified and inspected by various compiler passes. These 'Var.Var' names may either
21 -- be global or local, see "Var#globalvslocal"
23 -- * 'Var.Var': see "Var#name_types"
28 -- ** Simple construction
29 mkGlobalId, mkVanillaGlobal, mkVanillaGlobalWithInfo,
30 mkLocalId, mkLocalIdWithInfo, mkExportedLocalId,
31 mkSysLocal, mkSysLocalM, mkUserLocal, mkUserLocalM,
32 mkTemplateLocals, mkTemplateLocalsNum, mkTemplateLocal,
35 -- ** Taking an Id apart
36 idName, idType, idUnique, idInfo, idDetails,
38 recordSelectorFieldLabel,
41 setIdName, setIdUnique, Id.setIdType,
42 setIdExported, setIdNotExported,
43 globaliseId, localiseId,
44 setIdInfo, lazySetIdInfo, modifyIdInfo, maybeModifyIdInfo,
45 zapLamIdInfo, zapDemandIdInfo, zapFragileIdInfo, transferPolyIdInfo,
48 -- ** Predicates on Ids
49 isImplicitId, isDeadBinder, isDictId, isStrictId,
50 isExportedId, isLocalId, isGlobalId,
51 isRecordSelector, isNaughtyRecordSelector,
52 isClassOpId_maybe, isDFunId,
53 isPrimOpId, isPrimOpId_maybe,
54 isFCallId, isFCallId_maybe,
55 isDataConWorkId, isDataConWorkId_maybe, isDataConId_maybe, idDataCon,
56 isConLikeId, isBottomingId, idIsFrom,
57 isTickBoxOp, isTickBoxOp_maybe,
60 -- ** Inline pragma stuff
61 idInlinePragma, setInlinePragma, modifyInlinePragma,
62 idInlineActivation, setInlineActivation, idRuleMatchInfo,
64 -- ** One-shot lambdas
65 isOneShotBndr, isOneShotLambda, isStateHackType,
66 setOneShotLambda, clearOneShotLambda,
68 -- ** Reading 'IdInfo' fields
70 idNewDemandInfo, idNewDemandInfo_maybe,
71 idNewStrictness, idNewStrictness_maybe,
72 idUnfolding, realIdUnfolding,
73 idSpecialisation, idCoreRules, idHasRules,
84 -- ** Writing 'IdInfo' fields
88 setIdNewStrictness, zapIdNewStrictness,
91 setIdOccInfo, zapIdOccInfo,
100 #include "HsVersions.h"
102 import CoreSyn ( CoreRule, Unfolding( NoUnfolding ) )
107 -- Imported and re-exported
108 import Var( Var, Id, DictId,
109 idInfo, idDetails, globaliseId,
110 isId, isLocalId, isGlobalId, isExportedId )
117 #ifdef OLD_STRICTNESS
118 import qualified Demand
136 -- infixl so you can say (id `set` a `set` b)
137 infixl 1 `setIdUnfolding`,
139 `setIdNewDemandInfo`,
140 `setIdNewStrictness`,
141 `setIdSpecialisation`,
144 #ifdef OLD_STRICTNESS
151 %************************************************************************
153 \subsection{Basic Id manipulation}
155 %************************************************************************
161 idUnique :: Id -> Unique
162 idUnique = Var.varUnique
167 idPrimRep :: Id -> PrimRep
168 idPrimRep id = typePrimRep (idType id)
170 setIdName :: Id -> Name -> Id
171 setIdName = Var.setVarName
173 setIdUnique :: Id -> Unique -> Id
174 setIdUnique = Var.setVarUnique
176 -- | Not only does this set the 'Id' 'Type', it also evaluates the type to try and
177 -- reduce space usage
178 setIdType :: Id -> Type -> Id
179 setIdType id ty = seqType ty `seq` Var.setVarType id ty
181 setIdExported :: Id -> Id
182 setIdExported = Var.setIdExported
184 setIdNotExported :: Id -> Id
185 setIdNotExported = Var.setIdNotExported
187 localiseId :: Id -> Id
188 -- Make an with the same unique and type as the
189 -- incoming Id, but with an *Internal* Name and *LocalId* flavour
191 | isLocalId id && isInternalName name
194 = mkLocalIdWithInfo (localiseName name) (idType id) (idInfo id)
198 lazySetIdInfo :: Id -> IdInfo -> Id
199 lazySetIdInfo = Var.lazySetIdInfo
201 setIdInfo :: Id -> IdInfo -> Id
202 setIdInfo id info = seqIdInfo info `seq` (lazySetIdInfo id info)
203 -- Try to avoid spack leaks by seq'ing
205 modifyIdInfo :: (IdInfo -> IdInfo) -> Id -> Id
206 modifyIdInfo fn id = setIdInfo id (fn (idInfo id))
208 -- maybeModifyIdInfo tries to avoid unnecesary thrashing
209 maybeModifyIdInfo :: Maybe IdInfo -> Id -> Id
210 maybeModifyIdInfo (Just new_info) id = lazySetIdInfo id new_info
211 maybeModifyIdInfo Nothing id = id
214 %************************************************************************
216 \subsection{Simple Id construction}
218 %************************************************************************
220 Absolutely all Ids are made by mkId. It is just like Var.mkId,
221 but in addition it pins free-tyvar-info onto the Id's type,
222 where it can easily be found.
224 Note [Free type variables]
225 ~~~~~~~~~~~~~~~~~~~~~~~~~~
226 At one time we cached the free type variables of the type of an Id
227 at the root of the type in a TyNote. The idea was to avoid repeating
228 the free-type-variable calculation. But it turned out to slow down
229 the compiler overall. I don't quite know why; perhaps finding free
230 type variables of an Id isn't all that common whereas applying a
231 substitution (which changes the free type variables) is more common.
232 Anyway, we removed it in March 2008.
235 -- | For an explanation of global vs. local 'Id's, see "Var#globalvslocal"
236 mkGlobalId :: IdDetails -> Name -> Type -> IdInfo -> Id
237 mkGlobalId = Var.mkGlobalVar
239 -- | Make a global 'Id' without any extra information at all
240 mkVanillaGlobal :: Name -> Type -> Id
241 mkVanillaGlobal name ty = mkVanillaGlobalWithInfo name ty vanillaIdInfo
243 -- | Make a global 'Id' with no global information but some generic 'IdInfo'
244 mkVanillaGlobalWithInfo :: Name -> Type -> IdInfo -> Id
245 mkVanillaGlobalWithInfo = mkGlobalId VanillaId
248 -- | For an explanation of global vs. local 'Id's, see "Var#globalvslocal"
249 mkLocalId :: Name -> Type -> Id
250 mkLocalId name ty = mkLocalIdWithInfo name ty vanillaIdInfo
252 mkLocalIdWithInfo :: Name -> Type -> IdInfo -> Id
253 mkLocalIdWithInfo name ty info = Var.mkLocalVar VanillaId name ty info
254 -- Note [Free type variables]
256 -- | Create a local 'Id' that is marked as exported.
257 -- This prevents things attached to it from being removed as dead code.
258 mkExportedLocalId :: Name -> Type -> Id
259 mkExportedLocalId name ty = Var.mkExportedLocalVar VanillaId name ty vanillaIdInfo
260 -- Note [Free type variables]
263 -- | Create a system local 'Id'. These are local 'Id's (see "Var#globalvslocal")
264 -- that are created by the compiler out of thin air
265 mkSysLocal :: FastString -> Unique -> Type -> Id
266 mkSysLocal fs uniq ty = mkLocalId (mkSystemVarName uniq fs) ty
268 mkSysLocalM :: MonadUnique m => FastString -> Type -> m Id
269 mkSysLocalM fs ty = getUniqueM >>= (\uniq -> return (mkSysLocal fs uniq ty))
272 -- | Create a user local 'Id'. These are local 'Id's (see "Var#globalvslocal") with a name and location that the user might recognize
273 mkUserLocal :: OccName -> Unique -> Type -> SrcSpan -> Id
274 mkUserLocal occ uniq ty loc = mkLocalId (mkInternalName uniq occ loc) ty
276 mkUserLocalM :: MonadUnique m => OccName -> Type -> SrcSpan -> m Id
277 mkUserLocalM occ ty loc = getUniqueM >>= (\uniq -> return (mkUserLocal occ uniq ty loc))
281 Make some local @Ids@ for a template @CoreExpr@. These have bogus
282 @Uniques@, but that's OK because the templates are supposed to be
283 instantiated before use.
286 -- | Workers get local names. "CoreTidy" will externalise these if necessary
287 mkWorkerId :: Unique -> Id -> Type -> Id
288 mkWorkerId uniq unwrkr ty
289 = mkLocalId (mkDerivedInternalName mkWorkerOcc uniq (getName unwrkr)) ty
291 -- | Create a /template local/: a family of system local 'Id's in bijection with @Int@s, typically used in unfoldings
292 mkTemplateLocal :: Int -> Type -> Id
293 mkTemplateLocal i ty = mkSysLocal (fsLit "tpl") (mkBuiltinUnique i) ty
295 -- | Create a template local for a series of types
296 mkTemplateLocals :: [Type] -> [Id]
297 mkTemplateLocals = mkTemplateLocalsNum 1
299 -- | Create a template local for a series of type, but start from a specified template local
300 mkTemplateLocalsNum :: Int -> [Type] -> [Id]
301 mkTemplateLocalsNum n tys = zipWith mkTemplateLocal [n..] tys
305 %************************************************************************
307 \subsection{Special Ids}
309 %************************************************************************
312 -- | If the 'Id' is that for a record selector, extract the 'sel_tycon' and label. Panic otherwise
313 recordSelectorFieldLabel :: Id -> (TyCon, FieldLabel)
314 recordSelectorFieldLabel id
315 = case Var.idDetails id of
316 RecSelId { sel_tycon = tycon } -> (tycon, idName id)
317 _ -> panic "recordSelectorFieldLabel"
319 isRecordSelector :: Id -> Bool
320 isNaughtyRecordSelector :: Id -> Bool
321 isPrimOpId :: Id -> Bool
322 isFCallId :: Id -> Bool
323 isDataConWorkId :: Id -> Bool
324 isDFunId :: Id -> Bool
326 isClassOpId_maybe :: Id -> Maybe Class
327 isPrimOpId_maybe :: Id -> Maybe PrimOp
328 isFCallId_maybe :: Id -> Maybe ForeignCall
329 isDataConWorkId_maybe :: Id -> Maybe DataCon
331 isRecordSelector id = case Var.idDetails id of
335 isNaughtyRecordSelector id = case Var.idDetails id of
336 RecSelId { sel_naughty = n } -> n
339 isClassOpId_maybe id = case Var.idDetails id of
340 ClassOpId cls -> Just cls
343 isPrimOpId id = case Var.idDetails id of
347 isDFunId id = case Var.idDetails id of
351 isPrimOpId_maybe id = case Var.idDetails id of
352 PrimOpId op -> Just op
355 isFCallId id = case Var.idDetails id of
359 isFCallId_maybe id = case Var.idDetails id of
360 FCallId call -> Just call
363 isDataConWorkId id = case Var.idDetails id of
364 DataConWorkId _ -> True
367 isDataConWorkId_maybe id = case Var.idDetails id of
368 DataConWorkId con -> Just con
371 isDataConId_maybe :: Id -> Maybe DataCon
372 isDataConId_maybe id = case Var.idDetails id of
373 DataConWorkId con -> Just con
374 DataConWrapId con -> Just con
377 idDataCon :: Id -> DataCon
378 -- ^ Get from either the worker or the wrapper 'Id' to the 'DataCon'. Currently used only in the desugarer.
380 -- INVARIANT: @idDataCon (dataConWrapId d) = d@: remember, 'dataConWrapId' can return either the wrapper or the worker
381 idDataCon id = isDataConId_maybe id `orElse` pprPanic "idDataCon" (ppr id)
384 isDictId :: Id -> Bool
385 isDictId id = isDictTy (idType id)
387 hasNoBinding :: Id -> Bool
388 -- ^ Returns @True@ of an 'Id' which may not have a
389 -- binding, even though it is defined in this module.
391 -- Data constructor workers used to be things of this kind, but
392 -- they aren't any more. Instead, we inject a binding for
393 -- them at the CorePrep stage.
394 -- EXCEPT: unboxed tuples, which definitely have no binding
395 hasNoBinding id = case Var.idDetails id of
396 PrimOpId _ -> True -- See Note [Primop wrappers]
398 DataConWorkId dc -> isUnboxedTupleCon dc
401 isImplicitId :: Id -> Bool
402 -- ^ 'isImplicitId' tells whether an 'Id's info is implied by other
403 -- declarations, so we don't need to put its signature in an interface
404 -- file, even if it's mentioned in some other interface unfolding.
406 = case Var.idDetails id of
410 DataConWorkId {} -> True
411 DataConWrapId {} -> True
412 -- These are are implied by their type or class decl;
413 -- remember that all type and class decls appear in the interface file.
414 -- The dfun id is not an implicit Id; it must *not* be omitted, because
415 -- it carries version info for the instance decl
418 idIsFrom :: Module -> Id -> Bool
419 idIsFrom mod id = nameIsLocalOrFrom mod (idName id)
422 Note [Primop wrappers]
423 ~~~~~~~~~~~~~~~~~~~~~~
424 Currently hasNoBinding claims that PrimOpIds don't have a curried
425 function definition. But actually they do, in GHC.PrimopWrappers,
426 which is auto-generated from prelude/primops.txt.pp. So actually, hasNoBinding
427 could return 'False' for PrimOpIds.
429 But we'd need to add something in CoreToStg to swizzle any unsaturated
430 applications of GHC.Prim.plusInt# to GHC.PrimopWrappers.plusInt#.
432 Nota Bene: GHC.PrimopWrappers is needed *regardless*, because it's
433 used by GHCi, which does not implement primops direct at all.
438 isDeadBinder :: Id -> Bool
439 isDeadBinder bndr | isId bndr = isDeadOcc (idOccInfo bndr)
440 | otherwise = False -- TyVars count as not dead
444 isTickBoxOp :: Id -> Bool
446 case Var.idDetails id of
447 TickBoxOpId _ -> True
450 isTickBoxOp_maybe :: Id -> Maybe TickBoxOp
451 isTickBoxOp_maybe id =
452 case Var.idDetails id of
453 TickBoxOpId tick -> Just tick
457 %************************************************************************
459 \subsection{IdInfo stuff}
461 %************************************************************************
464 ---------------------------------
466 idArity :: Id -> Arity
467 idArity id = arityInfo (idInfo id)
469 setIdArity :: Id -> Arity -> Id
470 setIdArity id arity = modifyIdInfo (`setArityInfo` arity) id
472 #ifdef OLD_STRICTNESS
473 ---------------------------------
475 idStrictness :: Id -> StrictnessInfo
476 idStrictness id = strictnessInfo (idInfo id)
478 setIdStrictness :: Id -> StrictnessInfo -> Id
479 setIdStrictness id strict_info = modifyIdInfo (`setStrictnessInfo` strict_info) id
482 -- | Returns true if an application to n args would diverge
483 isBottomingId :: Id -> Bool
484 isBottomingId id = isBottomingSig (idNewStrictness id)
486 idNewStrictness_maybe :: Id -> Maybe StrictSig
487 idNewStrictness :: Id -> StrictSig
489 idNewStrictness_maybe id = newStrictnessInfo (idInfo id)
490 idNewStrictness id = idNewStrictness_maybe id `orElse` topSig
492 setIdNewStrictness :: Id -> StrictSig -> Id
493 setIdNewStrictness id sig = modifyIdInfo (`setNewStrictnessInfo` Just sig) id
495 zapIdNewStrictness :: Id -> Id
496 zapIdNewStrictness id = modifyIdInfo (`setNewStrictnessInfo` Nothing) id
498 -- | This predicate says whether the 'Id' has a strict demand placed on it or
499 -- has a type such that it can always be evaluated strictly (e.g., an
500 -- unlifted type, but see the comment for 'isStrictType'). We need to
501 -- check separately whether the 'Id' has a so-called \"strict type\" because if
502 -- the demand for the given @id@ hasn't been computed yet but @id@ has a strict
503 -- type, we still want @isStrictId id@ to be @True@.
504 isStrictId :: Id -> Bool
506 = ASSERT2( isId id, text "isStrictId: not an id: " <+> ppr id )
507 (isStrictDmd (idNewDemandInfo id)) ||
508 (isStrictType (idType id))
510 ---------------------------------
512 idUnfolding :: Id -> Unfolding
513 -- Do not expose the unfolding of a loop breaker!
515 | isNonRuleLoopBreaker (occInfo info) = NoUnfolding
516 | otherwise = unfoldingInfo info
520 realIdUnfolding :: Id -> Unfolding
521 -- Expose the unfolding if there is one, including for loop breakers
522 realIdUnfolding id = unfoldingInfo (idInfo id)
524 setIdUnfolding :: Id -> Unfolding -> Id
525 setIdUnfolding id unfolding = modifyIdInfo (`setUnfoldingInfo` unfolding) id
527 #ifdef OLD_STRICTNESS
528 ---------------------------------
530 idDemandInfo :: Id -> Demand.Demand
531 idDemandInfo id = demandInfo (idInfo id)
533 setIdDemandInfo :: Id -> Demand.Demand -> Id
534 setIdDemandInfo id demand_info = modifyIdInfo (`setDemandInfo` demand_info) id
537 idNewDemandInfo_maybe :: Id -> Maybe NewDemand.Demand
538 idNewDemandInfo :: Id -> NewDemand.Demand
540 idNewDemandInfo_maybe id = newDemandInfo (idInfo id)
541 idNewDemandInfo id = newDemandInfo (idInfo id) `orElse` NewDemand.topDmd
543 setIdNewDemandInfo :: Id -> NewDemand.Demand -> Id
544 setIdNewDemandInfo id dmd = modifyIdInfo (`setNewDemandInfo` Just dmd) id
546 ---------------------------------
549 -- See Note [Specialisations and RULES in IdInfo] in IdInfo.lhs
551 idSpecialisation :: Id -> SpecInfo
552 idSpecialisation id = specInfo (idInfo id)
554 idCoreRules :: Id -> [CoreRule]
555 idCoreRules id = specInfoRules (idSpecialisation id)
557 idHasRules :: Id -> Bool
558 idHasRules id = not (isEmptySpecInfo (idSpecialisation id))
560 setIdSpecialisation :: Id -> SpecInfo -> Id
561 setIdSpecialisation id spec_info = modifyIdInfo (`setSpecInfo` spec_info) id
563 ---------------------------------
565 idCafInfo :: Id -> CafInfo
566 #ifdef OLD_STRICTNESS
567 idCafInfo id = case cgInfo (idInfo id) of
568 NoCgInfo -> pprPanic "idCafInfo" (ppr id)
569 info -> cgCafInfo info
571 idCafInfo id = cafInfo (idInfo id)
574 setIdCafInfo :: Id -> CafInfo -> Id
575 setIdCafInfo id caf_info = modifyIdInfo (`setCafInfo` caf_info) id
577 ---------------------------------
579 #ifdef OLD_STRICTNESS
580 idCprInfo :: Id -> CprInfo
581 idCprInfo id = cprInfo (idInfo id)
583 setIdCprInfo :: Id -> CprInfo -> Id
584 setIdCprInfo id cpr_info = modifyIdInfo (`setCprInfo` cpr_info) id
587 ---------------------------------
589 idOccInfo :: Id -> OccInfo
590 idOccInfo id = occInfo (idInfo id)
592 setIdOccInfo :: Id -> OccInfo -> Id
593 setIdOccInfo id occ_info = modifyIdInfo (`setOccInfo` occ_info) id
595 zapIdOccInfo :: Id -> Id
596 zapIdOccInfo b = b `setIdOccInfo` NoOccInfo
600 ---------------------------------
602 The inline pragma tells us to be very keen to inline this Id, but it's still
603 OK not to if optimisation is switched off.
606 idInlinePragma :: Id -> InlinePragma
607 idInlinePragma id = inlinePragInfo (idInfo id)
609 setInlinePragma :: Id -> InlinePragma -> Id
610 setInlinePragma id prag = modifyIdInfo (`setInlinePragInfo` prag) id
612 modifyInlinePragma :: Id -> (InlinePragma -> InlinePragma) -> Id
613 modifyInlinePragma id fn = modifyIdInfo (\info -> info `setInlinePragInfo` (fn (inlinePragInfo info))) id
615 idInlineActivation :: Id -> Activation
616 idInlineActivation id = inlinePragmaActivation (idInlinePragma id)
618 setInlineActivation :: Id -> Activation -> Id
619 setInlineActivation id act = modifyInlinePragma id (\prag -> setInlinePragmaActivation prag act)
621 idRuleMatchInfo :: Id -> RuleMatchInfo
622 idRuleMatchInfo id = inlinePragmaRuleMatchInfo (idInlinePragma id)
624 isConLikeId :: Id -> Bool
625 isConLikeId id = isDataConWorkId id || isConLike (idRuleMatchInfo id)
629 ---------------------------------
632 idLBVarInfo :: Id -> LBVarInfo
633 idLBVarInfo id = lbvarInfo (idInfo id)
635 -- | Returns whether the lambda associated with the 'Id' is certainly applied at most once
636 -- OR we are applying the \"state hack\" which makes it appear as if theis is the case for
637 -- lambdas used in @IO@. You should prefer using this over 'isOneShotLambda'
638 isOneShotBndr :: Id -> Bool
639 -- This one is the "business end", called externally.
640 -- Its main purpose is to encapsulate the Horrible State Hack
641 isOneShotBndr id = isOneShotLambda id || isStateHackType (idType id)
643 -- | Should we apply the state hack to values of this 'Type'?
644 isStateHackType :: Type -> Bool
649 = case splitTyConApp_maybe ty of
650 Just (tycon,_) -> tycon == statePrimTyCon
652 -- This is a gross hack. It claims that
653 -- every function over realWorldStatePrimTy is a one-shot
654 -- function. This is pretty true in practice, and makes a big
655 -- difference. For example, consider
656 -- a `thenST` \ r -> ...E...
657 -- The early full laziness pass, if it doesn't know that r is one-shot
658 -- will pull out E (let's say it doesn't mention r) to give
659 -- let lvl = E in a `thenST` \ r -> ...lvl...
660 -- When `thenST` gets inlined, we end up with
661 -- let lvl = E in \s -> case a s of (r, s') -> ...lvl...
662 -- and we don't re-inline E.
664 -- It would be better to spot that r was one-shot to start with, but
665 -- I don't want to rely on that.
667 -- Another good example is in fill_in in PrelPack.lhs. We should be able to
668 -- spot that fill_in has arity 2 (and when Keith is done, we will) but we can't yet.
671 -- | Returns whether the lambda associated with the 'Id' is certainly applied at most once.
672 -- You probably want to use 'isOneShotBndr' instead
673 isOneShotLambda :: Id -> Bool
674 isOneShotLambda id = case idLBVarInfo id of
675 IsOneShotLambda -> True
678 setOneShotLambda :: Id -> Id
679 setOneShotLambda id = modifyIdInfo (`setLBVarInfo` IsOneShotLambda) id
681 clearOneShotLambda :: Id -> Id
682 clearOneShotLambda id
683 | isOneShotLambda id = modifyIdInfo (`setLBVarInfo` NoLBVarInfo) id
686 -- The OneShotLambda functions simply fiddle with the IdInfo flag
687 -- But watch out: this may change the type of something else
689 -- If we change the one-shot-ness of x, f's type changes
693 zapInfo :: (IdInfo -> Maybe IdInfo) -> Id -> Id
694 zapInfo zapper id = maybeModifyIdInfo (zapper (idInfo id)) id
696 zapLamIdInfo :: Id -> Id
697 zapLamIdInfo = zapInfo zapLamInfo
699 zapDemandIdInfo :: Id -> Id
700 zapDemandIdInfo = zapInfo zapDemandInfo
702 zapFragileIdInfo :: Id -> Id
703 zapFragileIdInfo = zapInfo zapFragileInfo
706 Note [transferPolyIdInfo]
707 ~~~~~~~~~~~~~~~~~~~~~~~~~
710 f = /\a. let g = rhs in ...
712 where g has interesting strictness information. Then if we float thus
717 we *do not* want to lose g's
718 * strictness information
720 * inline pragma (though that is bit more debatable)
722 It's simple to retain strictness and arity, but not so simple to retain
725 so we simply discard those. Sooner or later this may bite us.
727 This transfer is used in two places:
728 FloatOut (long-distance let-floating)
729 SimplUtils.abstractFloats (short-distance let-floating)
731 If we abstract wrt one or more *value* binders, we must modify the
732 arity and strictness info before transferring it. E.g.
736 + substitute (g' y) for g
737 Notice that g' has an arity one more than the original g
740 transferPolyIdInfo :: Id -- Original Id
741 -> [Var] -- Abstract wrt these variables
744 transferPolyIdInfo old_id abstract_wrt new_id
745 = modifyIdInfo transfer new_id
747 arity_increase = count isId abstract_wrt -- Arity increases by the
748 -- number of value binders
750 old_info = idInfo old_id
751 old_arity = arityInfo old_info
752 old_inline_prag = inlinePragInfo old_info
753 new_arity = old_arity + arity_increase
754 old_strictness = newStrictnessInfo old_info
755 new_strictness = fmap (increaseStrictSigArity arity_increase) old_strictness
757 transfer new_info = new_info `setNewStrictnessInfo` new_strictness
758 `setArityInfo` new_arity
759 `setInlinePragInfo` old_inline_prag