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
17 exactArity, atLeastArity, unknownArity,
18 arityInfo, setArityInfo, ppArityInfo, arityLowerBound,
21 StrictnessInfo(..), -- Non-abstract
22 workerExists, mkStrictnessInfo,
23 noStrictnessInfo, strictnessInfo,
24 ppStrictnessInfo, setStrictnessInfo,
25 isBottomingStrictness, appIsBottom,
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
112 %************************************************************************
114 \subsection[arity-IdInfo]{Arity info about an @Id@}
116 %************************************************************************
118 For locally-defined Ids, the code generator maintains its own notion
119 of their arities; so it should not be asking... (but other things
120 besides the code-generator need arity info!)
124 = UnknownArity -- No idea
125 | ArityExactly Int -- Arity is exactly this
126 | ArityAtLeast Int -- Arity is this or greater
128 exactArity = ArityExactly
129 atLeastArity = ArityAtLeast
130 unknownArity = UnknownArity
132 arityLowerBound :: ArityInfo -> Int
133 arityLowerBound UnknownArity = 0
134 arityLowerBound (ArityAtLeast n) = n
135 arityLowerBound (ArityExactly n) = n
138 ppArityInfo UnknownArity = empty
139 ppArityInfo (ArityExactly arity) = hsep [ptext SLIT("__A"), int arity]
140 ppArityInfo (ArityAtLeast arity) = hsep [ptext SLIT("__AL"), int arity]
143 %************************************************************************
145 \subsection{Inline-pragma information}
147 %************************************************************************
153 | IAmASpecPragmaId -- Used for spec-pragma Ids; don't discard or inline
155 | IWantToBeINLINEd -- User INLINE pragma
156 | IMustNotBeINLINEd -- User NOINLINE pragma
158 | IAmALoopBreaker -- Used by the occurrence analyser to mark loop-breakers
159 -- in a group of recursive definitions
161 | ICanSafelyBeINLINEd -- Used by the occurrence analyser to mark things
162 -- that manifesly occur once, not inside SCCs,
163 -- not in constructor arguments
165 OccInfo -- Says whether the occurrence is inside a lambda
166 -- If so, must only substitute WHNFs
168 Bool -- False <=> occurs in more than one case branch
169 -- If so, there's a code-duplication issue
171 | IAmDead -- Marks unused variables. Sometimes useful for
172 -- lambda and case-bound variables.
174 | IMustBeINLINEd -- Absolutely must inline; used for PrimOps and
175 -- constructors only.
177 instance Outputable InlinePragInfo where
178 ppr NoInlinePragInfo = empty
179 ppr IMustBeINLINEd = ptext SLIT("__UU")
180 ppr IWantToBeINLINEd = ptext SLIT("__U")
181 ppr IMustNotBeINLINEd = ptext SLIT("__Unot")
182 ppr IAmALoopBreaker = ptext SLIT("__Ux")
183 ppr IAmDead = ptext SLIT("__Ud")
184 ppr (ICanSafelyBeINLINEd InsideLam _) = ptext SLIT("__Ul")
185 ppr (ICanSafelyBeINLINEd _ _) = ptext SLIT("__Us")
186 ppr IAmASpecPragmaId = ptext SLIT("__US")
188 instance Show InlinePragInfo where
189 showsPrec p prag = showsPrecSDoc p (ppr prag)
192 The @IMustNotBeDiscarded@ exists only to make Ids that are
193 on the *LHS* of bindings created by SPECIALISE pragmas;
195 The SpecPragmaId is never itself mentioned; it
196 exists solely so that the specialiser will find
197 the call to f, and make specialised version of it.
198 The SpecPragmaId binding is discarded by the specialiser
199 when it gathers up overloaded calls.
200 Meanwhile, it is not discarded as dead code.
204 = StrictOcc -- Occurs syntactically strictly;
205 -- i.e. in a function position or case scrutinee
207 | LazyOcc -- Not syntactically strict (*even* that of a strict function)
208 -- or in a case branch where there's more than one alternative
210 | InsideLam -- Inside a non-linear lambda (that is, a lambda which
211 -- is sure to be instantiated only once).
212 -- Substituting a redex for this occurrence is
213 -- dangerous because it might duplicate work.
215 instance Outputable OccInfo where
216 ppr StrictOcc = text "s"
218 ppr InsideLam = text "l"
221 notInsideLambda :: OccInfo -> Bool
222 notInsideLambda StrictOcc = True
223 notInsideLambda LazyOcc = True
224 notInsideLambda InsideLam = False
227 %************************************************************************
229 \subsection[specialisation-IdInfo]{Specialisation info about an @Id@}
231 %************************************************************************
233 A @IdSpecEnv@ holds details of an @Id@'s specialisations.
236 type IdSpecEnv = SpecEnv CoreExpr
239 For example, if \tr{f}'s @SpecEnv@ contains the mapping:
241 [List a, b] ===> (\d -> f' a b)
243 then when we find an application of f to matching types, we simply replace
244 it by the matching RHS:
246 f (List Int) Bool ===> (\d -> f' Int Bool)
248 All the stuff about how many dictionaries to discard, and what types
249 to apply the specialised function to, are handled by the fact that the
250 SpecEnv contains a template for the result of the specialisation.
252 There is one more exciting case, which is dealt with in exactly the same
253 way. If the specialised value is unboxed then it is lifted at its
254 definition site and unlifted at its uses. For example:
256 pi :: forall a. Num a => a
258 might have a specialisation
260 [Int#] ===> (case pi' of Lift pi# -> pi#)
262 where pi' :: Lift Int# is the specialised version of pi.
265 %************************************************************************
267 \subsection[strictness-IdInfo]{Strictness info about an @Id@}
269 %************************************************************************
271 We specify the strictness of a function by giving information about
272 each of the ``wrapper's'' arguments (see the description about
273 worker/wrapper-style transformations in the PJ/Launchbury paper on
276 The list of @Demands@ specifies: (a)~the strictness properties
277 of a function's arguments; (b)~the {\em existence} of a ``worker''
278 version of the function; and (c)~the type signature of that worker (if
279 it exists); i.e. its calling convention.
285 | StrictnessInfo [Demand]
286 Bool -- True <=> the function diverges regardless of its arguments
287 -- Useful for "error" and other disguised variants thereof.
288 -- BUT NB: f = \x y. error "urk"
289 -- will have info SI [SS] True
290 -- but still (f) and (f 2) are not bot; only (f 3 2) is bot
292 Bool -- True <=> there is a worker. There might not be, even for a
293 -- strict function, because:
294 -- (a) the function might be small enough to inline,
295 -- so no need for w/w split
296 -- (b) the strictness info might be "SSS" or something, so no w/w split.
300 mkStrictnessInfo :: ([Demand], Bool) -> Bool -> StrictnessInfo
302 mkStrictnessInfo (xs, is_bot) has_wrkr
303 | all isLazy xs && not is_bot = NoStrictnessInfo -- Uninteresting
304 | otherwise = StrictnessInfo xs is_bot has_wrkr
306 noStrictnessInfo = NoStrictnessInfo
308 isBottomingStrictness (StrictnessInfo _ bot _) = bot
309 isBottomingStrictness NoStrictnessInfo = False
311 -- appIsBottom returns true if an application to n args would diverge
312 appIsBottom (StrictnessInfo ds bot _) n = bot && (n >= length ds)
313 appIsBottom NoStrictnessInfo n = False
315 ppStrictnessInfo NoStrictnessInfo = empty
316 ppStrictnessInfo (StrictnessInfo wrapper_args bot wrkr_maybe)
317 = hsep [ptext SLIT("__S"), pprDemands wrapper_args bot]
322 workerExists :: StrictnessInfo -> Bool
323 workerExists (StrictnessInfo _ _ worker_exists) = worker_exists
324 workerExists other = False
328 %************************************************************************
330 \subsection[update-IdInfo]{Update-analysis info about an @Id@}
332 %************************************************************************
337 | SomeUpdateInfo UpdateSpec
339 -- we need Eq/Ord to cross-chk update infos in interfaces
341 -- the form in which we pass update-analysis info between modules:
342 type UpdateSpec = [Int]
346 mkUpdateInfo = SomeUpdateInfo
348 updateInfoMaybe NoUpdateInfo = Nothing
349 updateInfoMaybe (SomeUpdateInfo []) = Nothing
350 updateInfoMaybe (SomeUpdateInfo u) = Just u
353 Text instance so that the update annotations can be read in.
356 ppUpdateInfo NoUpdateInfo = empty
357 ppUpdateInfo (SomeUpdateInfo []) = empty
358 ppUpdateInfo (SomeUpdateInfo spec) = (<>) (ptext SLIT("__U ")) (hcat (map int spec))
361 %************************************************************************
363 \subsection[CAF-IdInfo]{CAF-related information}
365 %************************************************************************
367 This information is used to build Static Reference Tables (see
368 simplStg/ComputeSRT.lhs).
372 = MayHaveCafRefs -- either:
373 -- (1) A function or static constructor
374 -- that refers to one or more CAFs,
375 -- (2) A real live CAF
377 | NoCafRefs -- A function or static constructor
378 -- that refers to no CAFs.
380 -- LATER: not sure how easy this is...
384 ppCafInfo NoCafRefs = ptext SLIT("__C")
385 ppCafInfo MayHaveCafRefs = empty