2 % (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
4 \section[IdInfo]{@IdInfos@: Non-essential information about @Ids@}
6 (And a pretty good illustration of quite a few things wrong with
11 GlobalIdDetails(..), notGlobalId, -- Not abstract
14 vanillaIdInfo, noCafIdInfo,
15 seqIdInfo, megaSeqIdInfo,
18 zapLamInfo, zapDemandInfo,
23 arityInfo, setArityInfo, ppArityInfo,
25 -- New demand and strictness info
26 newStrictnessInfo, setNewStrictnessInfo,
27 newDemandInfo, setNewDemandInfo, pprNewStrictness,
31 -- Strictness; imported from Demand
33 mkStrictnessInfo, noStrictnessInfo,
34 ppStrictnessInfo,isBottomingStrictness,
38 WorkerInfo(..), workerExists, wrapperArity, workerId,
39 workerInfo, setWorkerInfo, ppWorkerInfo,
42 unfoldingInfo, setUnfoldingInfo, setUnfoldingInfoLazily,
45 -- Old DemandInfo and StrictnessInfo
46 demandInfo, setDemandInfo,
47 strictnessInfo, setStrictnessInfo,
48 cprInfoFromNewStrictness,
49 oldStrictnessFromNew, newStrictnessFromOld,
52 -- Constructed Product Result Info
53 CprInfo(..), cprInfo, setCprInfo, ppCprInfo, noCprInfo,
58 inlinePragInfo, setInlinePragInfo,
61 OccInfo(..), isFragileOcc, isDeadOcc, isLoopBreaker,
62 InsideLam, OneBranch, insideLam, notInsideLam, oneBranch, notOneBranch,
66 SpecInfo(..), specInfo, setSpecInfo, isEmptySpecInfo,
67 specInfoFreeVars, specInfoRules, seqSpecInfo,
70 CafInfo(..), cafInfo, ppCafInfo, setCafInfo, mayHaveCafRefs,
72 -- Lambda-bound variable info
73 LBVarInfo(..), lbvarInfo, setLBVarInfo, noLBVarInfo, hasNoLBVarInfo
76 #include "HsVersions.h"
80 import Class ( Class )
81 import PrimOp ( PrimOp )
83 import VarSet ( VarSet, emptyVarSet, seqVarSet )
84 import BasicTypes ( OccInfo(..), isFragileOcc, isDeadOcc, seqOccInfo, isLoopBreaker,
85 InsideLam, insideLam, notInsideLam,
86 OneBranch, oneBranch, notOneBranch,
90 import DataCon ( DataCon )
91 import TyCon ( TyCon, FieldLabel )
92 import ForeignCall ( ForeignCall )
95 import Maybe ( isJust )
99 import Demand hiding( Demand, seqDemand )
100 import qualified Demand
101 import Util ( listLengthCmp )
102 import List ( replicate )
105 -- infixl so you can say (id `set` a `set` b)
106 infixl 1 `setSpecInfo`,
114 `setNewStrictnessInfo`,
115 `setAllStrictnessInfo`,
117 #ifdef OLD_STRICTNESS
120 , `setStrictnessInfo`
124 %************************************************************************
126 \subsection{New strictness info}
128 %************************************************************************
133 -- setAllStrictnessInfo :: IdInfo -> Maybe StrictSig -> IdInfo
134 -- Set old and new strictness info
135 setAllStrictnessInfo info Nothing
136 = info { newStrictnessInfo = Nothing
137 #ifdef OLD_STRICTNESS
138 , strictnessInfo = NoStrictnessInfo
139 , cprInfo = NoCPRInfo
143 setAllStrictnessInfo info (Just sig)
144 = info { newStrictnessInfo = Just sig
145 #ifdef OLD_STRICTNESS
146 , strictnessInfo = oldStrictnessFromNew sig
147 , cprInfo = cprInfoFromNewStrictness sig
151 seqNewStrictnessInfo Nothing = ()
152 seqNewStrictnessInfo (Just ty) = seqStrictSig ty
154 pprNewStrictness Nothing = empty
155 pprNewStrictness (Just sig) = ftext FSLIT("Str:") <+> ppr sig
157 #ifdef OLD_STRICTNESS
158 oldStrictnessFromNew :: StrictSig -> Demand.StrictnessInfo
159 oldStrictnessFromNew sig = mkStrictnessInfo (map oldDemand dmds, isBotRes res_info)
161 (dmds, res_info) = splitStrictSig sig
163 cprInfoFromNewStrictness :: StrictSig -> CprInfo
164 cprInfoFromNewStrictness sig = case strictSigResInfo sig of
168 newStrictnessFromOld :: Name -> Arity -> Demand.StrictnessInfo -> CprInfo -> StrictSig
169 newStrictnessFromOld name arity (Demand.StrictnessInfo ds res) cpr
170 | listLengthCmp ds arity /= GT -- length ds <= arity
171 -- Sometimes the old strictness analyser has more
172 -- demands than the arity justifies
173 = mk_strict_sig name arity $
174 mkTopDmdType (map newDemand ds) (newRes res cpr)
176 newStrictnessFromOld name arity other cpr
177 = -- Either no strictness info, or arity is too small
178 -- In either case we can't say anything useful
179 mk_strict_sig name arity $
180 mkTopDmdType (replicate arity lazyDmd) (newRes False cpr)
182 mk_strict_sig name arity dmd_ty
183 = WARN( arity /= dmdTypeDepth dmd_ty, ppr name <+> (ppr arity $$ ppr dmd_ty) )
186 newRes True _ = BotRes
187 newRes False ReturnsCPR = retCPR
188 newRes False NoCPRInfo = TopRes
190 newDemand :: Demand.Demand -> NewDemand.Demand
191 newDemand (WwLazy True) = Abs
192 newDemand (WwLazy False) = lazyDmd
193 newDemand WwStrict = evalDmd
194 newDemand (WwUnpack unpk ds) = Eval (Prod (map newDemand ds))
195 newDemand WwPrim = lazyDmd
196 newDemand WwEnum = evalDmd
198 oldDemand :: NewDemand.Demand -> Demand.Demand
199 oldDemand Abs = WwLazy True
200 oldDemand Top = WwLazy False
201 oldDemand Bot = WwStrict
202 oldDemand (Box Bot) = WwStrict
203 oldDemand (Box Abs) = WwLazy False
204 oldDemand (Box (Eval _)) = WwStrict -- Pass box only
205 oldDemand (Defer d) = WwLazy False
206 oldDemand (Eval (Prod ds)) = WwUnpack True (map oldDemand ds)
207 oldDemand (Eval (Poly _)) = WwStrict
208 oldDemand (Call _) = WwStrict
210 #endif /* OLD_STRICTNESS */
215 seqNewDemandInfo Nothing = ()
216 seqNewDemandInfo (Just dmd) = seqDemand dmd
220 %************************************************************************
222 \subsection{GlobalIdDetails
224 %************************************************************************
226 This type is here (rather than in Id.lhs) mainly because there's
227 an IdInfo.hi-boot, but no Id.hi-boot, and GlobalIdDetails is imported
228 (recursively) by Var.lhs.
232 = VanillaGlobal -- Imported from elsewhere, a default method Id.
234 | RecordSelId TyCon FieldLabel -- The Id for a record selector
236 | DataConWorkId DataCon -- The Id for a data constructor *worker*
237 | DataConWrapId DataCon -- The Id for a data constructor *wrapper*
238 -- [the only reasons we need to know is so that
239 -- a) we can suppress printing a definition in the interface file
240 -- b) when typechecking a pattern we can get from the
241 -- Id back to the data con]
243 | ClassOpId Class -- An operation of a class
245 | PrimOpId PrimOp -- The Id for a primitive operator
246 | FCallId ForeignCall -- The Id for a foreign call
248 | NotGlobalId -- Used as a convenient extra return value from globalIdDetails
250 notGlobalId = NotGlobalId
252 instance Outputable GlobalIdDetails where
253 ppr NotGlobalId = ptext SLIT("[***NotGlobalId***]")
254 ppr VanillaGlobal = ptext SLIT("[GlobalId]")
255 ppr (DataConWorkId _) = ptext SLIT("[DataCon]")
256 ppr (DataConWrapId _) = ptext SLIT("[DataConWrapper]")
257 ppr (ClassOpId _) = ptext SLIT("[ClassOp]")
258 ppr (PrimOpId _) = ptext SLIT("[PrimOp]")
259 ppr (FCallId _) = ptext SLIT("[ForeignCall]")
260 ppr (RecordSelId _ _) = ptext SLIT("[RecSel]")
264 %************************************************************************
266 \subsection{The main IdInfo type}
268 %************************************************************************
270 An @IdInfo@ gives {\em optional} information about an @Id@. If
271 present it never lies, but it may not be present, in which case there
272 is always a conservative assumption which can be made.
274 Two @Id@s may have different info even though they have the same
275 @Unique@ (and are hence the same @Id@); for example, one might lack
276 the properties attached to the other.
278 The @IdInfo@ gives information about the value, or definition, of the
279 @Id@. It does {\em not} contain information about the @Id@'s usage
280 (except for @DemandInfo@? ToDo). (@lbvarInfo@ is also a marginal
286 arityInfo :: !ArityInfo, -- Its arity
287 specInfo :: SpecInfo, -- Specialisations of this function which exist
288 #ifdef OLD_STRICTNESS
289 cprInfo :: CprInfo, -- Function always constructs a product result
290 demandInfo :: Demand.Demand, -- Whether or not it is definitely demanded
291 strictnessInfo :: StrictnessInfo, -- Strictness properties
293 workerInfo :: WorkerInfo, -- Pointer to Worker Function
294 -- Within one module this is irrelevant; the
295 -- inlining of a worker is handled via the Unfolding
296 -- WorkerInfo is used *only* to indicate the form of
297 -- the RHS, so that interface files don't actually
298 -- need to contain the RHS; it can be derived from
299 -- the strictness info
301 unfoldingInfo :: Unfolding, -- Its unfolding
302 cafInfo :: CafInfo, -- CAF info
303 lbvarInfo :: LBVarInfo, -- Info about a lambda-bound variable
304 inlinePragInfo :: InlinePragInfo, -- Inline pragma
305 occInfo :: OccInfo, -- How it occurs
307 newStrictnessInfo :: Maybe StrictSig, -- Reason for Maybe: the DmdAnal phase needs to
308 -- know whether whether this is the first visit,
309 -- so it can assign botSig. Other customers want
310 -- topSig. So Nothing is good.
312 newDemandInfo :: Maybe Demand -- Similarly we want to know if there's no
313 -- known demand yet, for when we are looking for
317 seqIdInfo :: IdInfo -> ()
318 seqIdInfo (IdInfo {}) = ()
320 megaSeqIdInfo :: IdInfo -> ()
322 = seqSpecInfo (specInfo info) `seq`
323 seqWorker (workerInfo info) `seq`
325 -- Omitting this improves runtimes a little, presumably because
326 -- some unfoldings are not calculated at all
327 -- seqUnfolding (unfoldingInfo info) `seq`
329 seqNewDemandInfo (newDemandInfo info) `seq`
330 seqNewStrictnessInfo (newStrictnessInfo info) `seq`
332 #ifdef OLD_STRICTNESS
333 Demand.seqDemand (demandInfo info) `seq`
334 seqStrictnessInfo (strictnessInfo info) `seq`
335 seqCpr (cprInfo info) `seq`
338 seqCaf (cafInfo info) `seq`
339 seqLBVar (lbvarInfo info) `seq`
340 seqOccInfo (occInfo info)
346 setWorkerInfo info wk = wk `seq` info { workerInfo = wk }
347 setSpecInfo info sp = sp `seq` info { specInfo = sp }
348 setInlinePragInfo info pr = pr `seq` info { inlinePragInfo = pr }
349 setOccInfo info oc = oc `seq` info { occInfo = oc }
350 #ifdef OLD_STRICTNESS
351 setStrictnessInfo info st = st `seq` info { strictnessInfo = st }
353 -- Try to avoid spack leaks by seq'ing
355 setUnfoldingInfoLazily info uf -- Lazy variant to avoid looking at the
356 = -- unfolding of an imported Id unless necessary
357 info { unfoldingInfo = uf } -- (In this case the demand-zapping is redundant.)
359 setUnfoldingInfo info uf
360 -- We do *not* seq on the unfolding info, For some reason, doing so
361 -- actually increases residency significantly.
362 = info { unfoldingInfo = uf }
364 #ifdef OLD_STRICTNESS
365 setDemandInfo info dd = info { demandInfo = dd }
366 setCprInfo info cp = info { cprInfo = cp }
369 setArityInfo info ar = info { arityInfo = ar }
370 setCafInfo info caf = info { cafInfo = caf }
372 setLBVarInfo info lb = {-lb `seq`-} info { lbvarInfo = lb }
374 setNewDemandInfo info dd = dd `seq` info { newDemandInfo = dd }
375 setNewStrictnessInfo info dd = dd `seq` info { newStrictnessInfo = dd }
380 vanillaIdInfo :: IdInfo
383 cafInfo = vanillaCafInfo,
384 arityInfo = unknownArity,
385 #ifdef OLD_STRICTNESS
388 strictnessInfo = NoStrictnessInfo,
390 specInfo = emptySpecInfo,
391 workerInfo = NoWorker,
392 unfoldingInfo = noUnfolding,
393 lbvarInfo = NoLBVarInfo,
394 inlinePragInfo = AlwaysActive,
396 newDemandInfo = Nothing,
397 newStrictnessInfo = Nothing
400 noCafIdInfo = vanillaIdInfo `setCafInfo` NoCafRefs
401 -- Used for built-in type Ids in MkId.
405 %************************************************************************
407 \subsection[arity-IdInfo]{Arity info about an @Id@}
409 %************************************************************************
411 For locally-defined Ids, the code generator maintains its own notion
412 of their arities; so it should not be asking... (but other things
413 besides the code-generator need arity info!)
416 type ArityInfo = Arity
417 -- A partial application of this Id to up to n-1 value arguments
418 -- does essentially no work. That is not necessarily the
419 -- same as saying that it has n leading lambdas, because coerces
420 -- may get in the way.
422 -- The arity might increase later in the compilation process, if
423 -- an extra lambda floats up to the binding site.
425 unknownArity = 0 :: Arity
427 ppArityInfo 0 = empty
428 ppArityInfo n = hsep [ptext SLIT("Arity"), int n]
431 %************************************************************************
433 \subsection{Inline-pragma information}
435 %************************************************************************
438 type InlinePragInfo = Activation
439 -- Tells when the inlining is active
440 -- When it is active the thing may be inlined, depending on how
443 -- If there was an INLINE pragma, then as a separate matter, the
444 -- RHS will have been made to look small with a CoreSyn Inline Note
448 %************************************************************************
452 %************************************************************************
455 -- CoreRules is used only in an idSpecialisation (move to IdInfo?)
457 = SpecInfo [CoreRule] VarSet -- Locally-defined free vars of RHSs
459 emptySpecInfo :: SpecInfo
460 emptySpecInfo = SpecInfo [] emptyVarSet
462 isEmptySpecInfo :: SpecInfo -> Bool
463 isEmptySpecInfo (SpecInfo rs _) = null rs
465 specInfoFreeVars :: SpecInfo -> VarSet
466 specInfoFreeVars (SpecInfo _ fvs) = fvs
468 specInfoRules :: SpecInfo -> [CoreRule]
469 specInfoRules (SpecInfo rules _) = rules
471 seqSpecInfo (SpecInfo rules fvs) = seqRules rules `seq` seqVarSet fvs
475 %************************************************************************
477 \subsection[worker-IdInfo]{Worker info about an @Id@}
479 %************************************************************************
481 If this Id has a worker then we store a reference to it. Worker
482 functions are generated by the worker/wrapper pass. This uses
483 information from strictness analysis.
485 There might not be a worker, even for a strict function, because:
486 (a) the function might be small enough to inline, so no need
488 (b) the strictness info might be "SSS" or something, so no w/w split.
490 Sometimes the arity of a wrapper changes from the original arity from
491 which it was generated, so we always emit the "original" arity into
492 the interface file, as part of the worker info.
494 How can this happen? Sometimes we get
495 f = coerce t (\x y -> $wf x y)
496 at the moment of w/w split; but the eta reducer turns it into
498 which is perfectly fine except that the exposed arity so far as
499 the code generator is concerned (zero) differs from the arity
500 when we did the split (2).
502 All this arises because we use 'arity' to mean "exactly how many
503 top level lambdas are there" in interface files; but during the
504 compilation of this module it means "how many things can I apply
509 data WorkerInfo = NoWorker
511 -- The Arity is the arity of the *wrapper* at the moment of the
512 -- w/w split. See notes above.
514 seqWorker :: WorkerInfo -> ()
515 seqWorker (HasWorker id a) = id `seq` a `seq` ()
516 seqWorker NoWorker = ()
518 ppWorkerInfo NoWorker = empty
519 ppWorkerInfo (HasWorker wk_id _) = ptext SLIT("Worker") <+> ppr wk_id
521 workerExists :: WorkerInfo -> Bool
522 workerExists NoWorker = False
523 workerExists (HasWorker _ _) = True
525 workerId :: WorkerInfo -> Id
526 workerId (HasWorker id _) = id
528 wrapperArity :: WorkerInfo -> Arity
529 wrapperArity (HasWorker _ a) = a
533 %************************************************************************
535 \subsection[CG-IdInfo]{Code generator-related information}
537 %************************************************************************
540 -- CafInfo is used to build Static Reference Tables (see simplStg/SRT.lhs).
543 = MayHaveCafRefs -- either:
544 -- (1) A function or static constructor
545 -- that refers to one or more CAFs,
546 -- (2) A real live CAF
548 | NoCafRefs -- A function or static constructor
549 -- that refers to no CAFs.
551 vanillaCafInfo = MayHaveCafRefs -- Definitely safe
553 mayHaveCafRefs MayHaveCafRefs = True
554 mayHaveCafRefs _ = False
556 seqCaf c = c `seq` ()
558 ppCafInfo NoCafRefs = ptext SLIT("NoCafRefs")
559 ppCafInfo MayHaveCafRefs = empty
562 %************************************************************************
564 \subsection[cpr-IdInfo]{Constructed Product Result info about an @Id@}
566 %************************************************************************
568 If the @Id@ is a function then it may have CPR info. A CPR analysis
569 phase detects whether:
573 The function's return value has a product type, i.e. an algebraic type
574 with a single constructor. Examples of such types are tuples and boxed
577 The function always 'constructs' the value that it is returning. It
578 must do this on every path through, and it's OK if it calls another
579 function which constructs the result.
582 If this is the case then we store a template which tells us the
583 function has the CPR property and which components of the result are
587 #ifdef OLD_STRICTNESS
590 | ReturnsCPR -- Yes, this function returns a constructed product
591 -- Implicitly, this means "after the function has been applied
592 -- to all its arguments", so the worker/wrapper builder in
593 -- WwLib.mkWWcpr checks that that it is indeed saturated before
594 -- making use of the CPR info
596 -- We used to keep nested info about sub-components, but
597 -- we never used it so I threw it away
599 seqCpr :: CprInfo -> ()
600 seqCpr ReturnsCPR = ()
601 seqCpr NoCPRInfo = ()
603 noCprInfo = NoCPRInfo
605 ppCprInfo NoCPRInfo = empty
606 ppCprInfo ReturnsCPR = ptext SLIT("__M")
608 instance Outputable CprInfo where
611 instance Show CprInfo where
612 showsPrec p c = showsPrecSDoc p (ppr c)
617 %************************************************************************
619 \subsection[lbvar-IdInfo]{Lambda-bound var info about an @Id@}
621 %************************************************************************
623 If the @Id@ is a lambda-bound variable then it may have lambda-bound
624 var info. Sometimes we know whether the lambda binding this var is a
625 ``one-shot'' lambda; that is, whether it is applied at most once.
627 This information may be useful in optimisation, as computations may
628 safely be floated inside such a lambda without risk of duplicating
632 data LBVarInfo = NoLBVarInfo
633 | IsOneShotLambda -- The lambda is applied at most once).
635 seqLBVar l = l `seq` ()
639 hasNoLBVarInfo NoLBVarInfo = True
640 hasNoLBVarInfo IsOneShotLambda = False
642 noLBVarInfo = NoLBVarInfo
644 pprLBVarInfo NoLBVarInfo = empty
645 pprLBVarInfo IsOneShotLambda = ptext SLIT("OneShot")
647 instance Outputable LBVarInfo where
650 instance Show LBVarInfo where
651 showsPrec p c = showsPrecSDoc p (ppr c)
655 %************************************************************************
657 \subsection{Bulk operations on IdInfo}
659 %************************************************************************
661 @zapLamInfo@ is used for lambda binders that turn out to to be
662 part of an unsaturated lambda
665 zapLamInfo :: IdInfo -> Maybe IdInfo
666 zapLamInfo info@(IdInfo {occInfo = occ, newDemandInfo = demand})
667 | is_safe_occ occ && is_safe_dmd demand
670 = Just (info {occInfo = safe_occ, newDemandInfo = Nothing})
672 -- The "unsafe" occ info is the ones that say I'm not in a lambda
673 -- because that might not be true for an unsaturated lambda
674 is_safe_occ (OneOcc in_lam once) = in_lam
675 is_safe_occ other = True
677 safe_occ = case occ of
678 OneOcc _ once -> OneOcc insideLam once
681 is_safe_dmd Nothing = True
682 is_safe_dmd (Just dmd) = not (isStrictDmd dmd)
686 zapDemandInfo :: IdInfo -> Maybe IdInfo
687 zapDemandInfo info@(IdInfo {newDemandInfo = dmd})
688 | isJust dmd = Just (info {newDemandInfo = Nothing})
689 | otherwise = Nothing