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
18 exactArity, atLeastArity, unknownArity,
19 arityInfo, setArityInfo, ppArityInfo, arityLowerBound,
22 StrictnessInfo(..), -- Non-abstract
23 workerExists, mkStrictnessInfo, mkBottomStrictnessInfo,
24 noStrictnessInfo, bottomIsGuaranteed, strictnessInfo,
25 ppStrictnessInfo, setStrictnessInfo,
28 unfoldingInfo, setUnfoldingInfo,
31 demandInfo, setDemandInfo,
34 InlinePragInfo(..), OccInfo(..),
35 inlinePragInfo, setInlinePragInfo, notInsideLambda,
38 IdSpecEnv, specInfo, setSpecInfo,
41 UpdateInfo, UpdateSpec,
42 mkUpdateInfo, updateInfo, updateInfoMaybe, ppUpdateInfo, setUpdateInfo,
45 CafInfo(..), cafInfo, setCafInfo, ppCafInfo,
48 #include "HsVersions.h"
51 import {-# SOURCE #-} CoreUnfold ( Unfolding, noUnfolding )
52 import {-# SOURCE #-} CoreSyn ( CoreExpr )
54 import SpecEnv ( SpecEnv, emptySpecEnv )
55 import Demand ( Demand, isLazy, wwLazy, pprDemands )
59 An @IdInfo@ gives {\em optional} information about an @Id@. If
60 present it never lies, but it may not be present, in which case there
61 is always a conservative assumption which can be made.
63 Two @Id@s may have different info even though they have the same
64 @Unique@ (and are hence the same @Id@); for example, one might lack
65 the properties attached to the other.
67 The @IdInfo@ gives information about the value, or definition, of the
68 @Id@. It does {\em not} contain information about the @Id@'s usage
69 (except for @DemandInfo@? ToDo).
74 arityInfo :: ArityInfo, -- Its arity
75 demandInfo :: Demand, -- Whether or not it is definitely demanded
76 specInfo :: IdSpecEnv, -- Specialisations of this function which exist
77 strictnessInfo :: StrictnessInfo, -- Strictness properties
78 unfoldingInfo :: Unfolding, -- Its unfolding
79 updateInfo :: UpdateInfo, -- Which args should be updated
81 inlinePragInfo :: !InlinePragInfo -- Inline pragmas
88 setUpdateInfo ud info = info { updateInfo = ud }
89 setDemandInfo dd info = info { demandInfo = dd }
90 setStrictnessInfo st info = info { strictnessInfo = st }
91 setSpecInfo sp info = info { specInfo = sp }
92 setArityInfo ar info = info { arityInfo = ar }
93 setInlinePragInfo pr info = info { inlinePragInfo = pr }
94 setUnfoldingInfo uf info = info { unfoldingInfo = uf }
95 setCafInfo cf info = info { cafInfo = cf }
101 arityInfo = UnknownArity,
103 specInfo = emptySpecEnv,
104 strictnessInfo = NoStrictnessInfo,
105 unfoldingInfo = noUnfolding,
106 updateInfo = NoUpdateInfo,
107 cafInfo = MayHaveCafRefs,
108 inlinePragInfo = NoInlinePragInfo
113 ppIdInfo :: IdInfo -> SDoc
114 ppIdInfo (IdInfo {arityInfo,
123 ppArityInfo arityInfo,
124 ppUpdateInfo updateInfo,
125 ppStrictnessInfo strictnessInfo,
128 -- Inline pragma printed out with all binders; see PprCore.pprIdBndr
132 %************************************************************************
134 \subsection[arity-IdInfo]{Arity info about an @Id@}
136 %************************************************************************
138 For locally-defined Ids, the code generator maintains its own notion
139 of their arities; so it should not be asking... (but other things
140 besides the code-generator need arity info!)
144 = UnknownArity -- No idea
145 | ArityExactly Int -- Arity is exactly this
146 | ArityAtLeast Int -- Arity is this or greater
148 exactArity = ArityExactly
149 atLeastArity = ArityAtLeast
150 unknownArity = UnknownArity
152 arityLowerBound :: ArityInfo -> Int
153 arityLowerBound UnknownArity = 0
154 arityLowerBound (ArityAtLeast n) = n
155 arityLowerBound (ArityExactly n) = n
158 ppArityInfo UnknownArity = empty
159 ppArityInfo (ArityExactly arity) = hsep [ptext SLIT("__A"), int arity]
160 ppArityInfo (ArityAtLeast arity) = hsep [ptext SLIT("__AL"), int arity]
163 %************************************************************************
165 \subsection{Inline-pragma information}
167 %************************************************************************
173 | IAmASpecPragmaId -- Used for spec-pragma Ids; don't discard or inline
175 | IWantToBeINLINEd -- User INLINE pragma
176 | IMustNotBeINLINEd -- User NOINLINE pragma
178 | IAmALoopBreaker -- Used by the occurrence analyser to mark loop-breakers
179 -- in a group of recursive definitions
181 | ICanSafelyBeINLINEd -- Used by the occurrence analyser to mark things
182 -- that manifesly occur once, not inside SCCs,
183 -- not in constructor arguments
185 OccInfo -- Says whether the occurrence is inside a lambda
186 -- If so, must only substitute WHNFs
188 Bool -- False <=> occurs in more than one case branch
189 -- If so, there's a code-duplication issue
191 | IAmDead -- Marks unused variables. Sometimes useful for
192 -- lambda and case-bound variables.
194 | IMustBeINLINEd -- Absolutely must inline; used for PrimOps and
195 -- constructors only.
197 instance Outputable InlinePragInfo where
198 ppr NoInlinePragInfo = empty
199 ppr IMustBeINLINEd = ptext SLIT("__UU")
200 ppr IWantToBeINLINEd = ptext SLIT("__U")
201 ppr IMustNotBeINLINEd = ptext SLIT("__Unot")
202 ppr IAmALoopBreaker = ptext SLIT("__Ux")
203 ppr IAmDead = ptext SLIT("__Ud")
204 ppr (ICanSafelyBeINLINEd _ _) = ptext SLIT("__Us")
205 ppr IAmASpecPragmaId = ptext SLIT("__US")
207 instance Show InlinePragInfo where
208 showsPrec p prag = showsPrecSDoc p (ppr prag)
211 The @IMustNotBeDiscarded@ exists only to make Ids that are
212 on the *LHS* of bindings created by SPECIALISE pragmas;
214 The SpecPragmaId is never itself mentioned; it
215 exists solely so that the specialiser will find
216 the call to f, and make specialised version of it.
217 The SpecPragmaId binding is discarded by the specialiser
218 when it gathers up overloaded calls.
219 Meanwhile, it is not discarded as dead code.
223 = StrictOcc -- Occurs syntactically strictly;
224 -- i.e. in a function position or case scrutinee
226 | LazyOcc -- Not syntactically strict (*even* that of a strict function)
227 -- or in a case branch where there's more than one alternative
229 | InsideLam -- Inside a non-linear lambda (that is, a lambda which
230 -- is sure to be instantiated only once).
231 -- Substituting a redex for this occurrence is
232 -- dangerous because it might duplicate work.
234 instance Outputable OccInfo where
235 ppr StrictOcc = text "s"
237 ppr InsideLam = text "l"
240 notInsideLambda :: OccInfo -> Bool
241 notInsideLambda StrictOcc = True
242 notInsideLambda LazyOcc = True
243 notInsideLambda InsideLam = False
246 %************************************************************************
248 \subsection[specialisation-IdInfo]{Specialisation info about an @Id@}
250 %************************************************************************
252 A @IdSpecEnv@ holds details of an @Id@'s specialisations.
255 type IdSpecEnv = SpecEnv CoreExpr
258 For example, if \tr{f}'s @SpecEnv@ contains the mapping:
260 [List a, b] ===> (\d -> f' a b)
262 then when we find an application of f to matching types, we simply replace
263 it by the matching RHS:
265 f (List Int) Bool ===> (\d -> f' Int Bool)
267 All the stuff about how many dictionaries to discard, and what types
268 to apply the specialised function to, are handled by the fact that the
269 SpecEnv contains a template for the result of the specialisation.
271 There is one more exciting case, which is dealt with in exactly the same
272 way. If the specialised value is unboxed then it is lifted at its
273 definition site and unlifted at its uses. For example:
275 pi :: forall a. Num a => a
277 might have a specialisation
279 [Int#] ===> (case pi' of Lift pi# -> pi#)
281 where pi' :: Lift Int# is the specialised version of pi.
285 %************************************************************************
287 \subsection[strictness-IdInfo]{Strictness info about an @Id@}
289 %************************************************************************
291 We specify the strictness of a function by giving information about
292 each of the ``wrapper's'' arguments (see the description about
293 worker/wrapper-style transformations in the PJ/Launchbury paper on
296 The list of @Demands@ specifies: (a)~the strictness properties
297 of a function's arguments; (b)~the {\em existence} of a ``worker''
298 version of the function; and (c)~the type signature of that worker (if
299 it exists); i.e. its calling convention.
305 | BottomGuaranteed -- This Id guarantees never to return;
306 -- it is bottom regardless of its arguments.
307 -- Useful for "error" and other disguised
310 | StrictnessInfo [Demand]
311 Bool -- True <=> there is a worker. There might not be, even for a
312 -- strict function, because:
313 -- (a) the function might be small enough to inline,
314 -- so no need for w/w split
315 -- (b) the strictness info might be "SSS" or something, so no w/w split.
317 -- Worker's Id, if applicable, and a list of the constructors
318 -- mentioned by the wrapper. This is necessary so that the
319 -- renamer can slurp them in. Without this info, the renamer doesn't
320 -- know which data types to slurp in concretely. Remember, for
321 -- strict things we don't put the unfolding in the interface file, to save space.
322 -- This constructor list allows the renamer to behave much as if the
323 -- unfolding *was* in the interface file.
327 mkStrictnessInfo :: [Demand] -> Bool -> StrictnessInfo
329 mkStrictnessInfo xs has_wrkr
330 | all isLazy xs = NoStrictnessInfo -- Uninteresting
331 | otherwise = StrictnessInfo xs has_wrkr
333 noStrictnessInfo = NoStrictnessInfo
334 mkBottomStrictnessInfo = BottomGuaranteed
336 bottomIsGuaranteed BottomGuaranteed = True
337 bottomIsGuaranteed other = False
339 ppStrictnessInfo NoStrictnessInfo = empty
340 ppStrictnessInfo BottomGuaranteed = ptext SLIT("__bot")
342 ppStrictnessInfo (StrictnessInfo wrapper_args wrkr_maybe)
343 = hsep [ptext SLIT("__S"), pprDemands wrapper_args]
348 workerExists :: StrictnessInfo -> Bool
349 workerExists (StrictnessInfo _ worker_exists) = worker_exists
350 workerExists other = False
354 %************************************************************************
356 \subsection[update-IdInfo]{Update-analysis info about an @Id@}
358 %************************************************************************
363 | SomeUpdateInfo UpdateSpec
365 -- we need Eq/Ord to cross-chk update infos in interfaces
367 -- the form in which we pass update-analysis info between modules:
368 type UpdateSpec = [Int]
372 mkUpdateInfo = SomeUpdateInfo
374 updateInfoMaybe NoUpdateInfo = Nothing
375 updateInfoMaybe (SomeUpdateInfo []) = Nothing
376 updateInfoMaybe (SomeUpdateInfo u) = Just u
379 Text instance so that the update annotations can be read in.
382 ppUpdateInfo NoUpdateInfo = empty
383 ppUpdateInfo (SomeUpdateInfo []) = empty
384 ppUpdateInfo (SomeUpdateInfo spec) = (<>) (ptext SLIT("__U ")) (hcat (map int spec))
387 %************************************************************************
389 \subsection[CAF-IdInfo]{CAF-related information}
391 %************************************************************************
393 This information is used to build Static Reference Tables (see
394 simplStg/ComputeSRT.lhs).
398 = MayHaveCafRefs -- either:
399 -- (1) A function or static constructor
400 -- that refers to one or more CAFs,
401 -- (2) A real live CAF
403 | NoCafRefs -- A function or static constructor
404 -- that refers to no CAFs.
406 -- LATER: not sure how easy this is...
410 ppCafInfo NoCafRefs = ptext SLIT("__C")
411 ppCafInfo MayHaveCafRefs = empty