2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section{Tidying up Core}
7 module TidyPgm( tidyCorePgm, tidyCoreExpr ) where
9 #include "HsVersions.h"
11 import CmdLineOpts ( DynFlag(..), dopt )
13 import CoreUnfold ( noUnfolding, mkTopUnfolding )
14 import CoreFVs ( ruleLhsFreeIds, ruleRhsFreeVars, exprSomeFreeVars )
15 import CoreTidy ( tidyExpr, tidyVarOcc, tidyIdRules )
16 import PprCore ( pprIdRules )
17 import CoreLint ( showPass, endPass )
18 import CoreUtils ( exprArity, rhsIsStatic )
21 import Var ( Id, Var )
22 import Id ( idType, idInfo, idName, idCoreRules,
23 isExportedId, mkVanillaGlobal, isLocalId,
24 isImplicitId, idArity, setIdInfo, idCafInfo
26 import IdInfo {- loads of stuff -}
27 import NewDemand ( isBottomingSig, topSig )
28 import BasicTypes ( Arity, isNeverActive )
29 import Name ( Name, getOccName, nameOccName, mkInternalName,
30 localiseName, isExternalName, nameSrcLoc, nameParent_maybe
32 import IfaceEnv ( allocateGlobalBinder )
33 import NameEnv ( lookupNameEnv, filterNameEnv )
34 import OccName ( TidyOccEnv, initTidyOccEnv, tidyOccName )
35 import Type ( tidyTopType )
36 import Module ( Module )
37 import HscTypes ( HscEnv(..), NameCache( nsUniqs ),
38 TypeEnv, extendTypeEnvList, typeEnvIds,
39 ModGuts(..), ModGuts, TyThing(..)
41 import Maybes ( orElse )
42 import ErrUtils ( showPass, dumpIfSet_core )
43 import UniqFM ( mapUFM )
44 import UniqSupply ( splitUniqSupply, uniqFromSupply )
45 import List ( partition )
46 import Maybe ( isJust )
48 import DATA_IOREF ( IORef, readIORef, writeIORef )
49 import FastTypes hiding ( fastOr )
53 %************************************************************************
55 \subsection{What goes on}
57 %************************************************************************
63 Step 1: Figure out external Ids
64 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
65 First we figure out which Ids are "external" Ids. An
66 "external" Id is one that is visible from outside the compilation
68 a) the user exported ones
69 b) ones mentioned in the unfoldings, workers,
70 or rules of externally-visible ones
71 This exercise takes a sweep of the bindings bottom to top. Actually,
72 in Step 2 we're also going to need to know which Ids should be
73 exported with their unfoldings, so we produce not an IdSet but an
77 Step 2: Tidy the program
78 ~~~~~~~~~~~~~~~~~~~~~~~~
79 Next we traverse the bindings top to bottom. For each *top-level*
82 1. Make it into a GlobalId
84 2. Give it a system-wide Unique.
85 [Even non-exported things need system-wide Uniques because the
86 byte-code generator builds a single Name->BCO symbol table.]
88 We use the NameCache kept in the HscEnv as the
89 source of such system-wide uniques.
91 For external Ids, use the original-name cache in the NameCache
92 to ensure that the unique assigned is the same as the Id had
93 in any previous compilation run.
95 3. If it's an external Id, make it have a global Name, otherwise
96 make it have a local Name.
97 This is used by the code generator to decide whether
98 to make the label externally visible
100 4. Give external Ids a "tidy" occurrence name. This means
101 we can print them in interface files without confusing
102 "x" (unique 5) with "x" (unique 10).
104 5. Give it its UTTERLY FINAL IdInfo; in ptic,
105 * Its IdDetails becomes VanillaGlobal, reflecting the fact that
106 from now on we regard it as a global, not local, Id
108 * its unfolding, if it should have one
110 * its arity, computed from the number of visible lambdas
112 * its CAF info, computed from what is free in its RHS
115 Finally, substitute these new top-level binders consistently
116 throughout, including in unfoldings. We also tidy binders in
117 RHSs, so that they print nicely in interfaces.
120 tidyCorePgm :: HscEnv -> ModGuts -> IO ModGuts
123 mod_impl@(ModGuts { mg_module = mod,
124 mg_types = env_tc, mg_insts = insts_tc,
125 mg_binds = binds_in, mg_rules = orphans_in })
126 = do { let { dflags = hsc_dflags hsc_env
127 ; nc_var = hsc_NC hsc_env }
128 ; showPass dflags "Tidy Core"
130 ; let omit_iface_prags = dopt Opt_OmitInterfacePragmas dflags
131 ; let ext_ids = findExternalSet omit_iface_prags binds_in orphans_in
132 ; let ext_rules = findExternalRules omit_iface_prags binds_in orphans_in ext_ids
133 -- findExternalRules filters ext_rules to avoid binders that
134 -- aren't externally visible; but the externally-visible binders
135 -- are computed (by findExternalSet) assuming that all orphan
136 -- rules are exported. So in fact we may export more than we
137 -- need. (It's a sort of mutual recursion.)
139 -- We also make sure to avoid any exported binders. Consider
140 -- f{-u1-} = 1 -- Local decl
142 -- f{-u2-} = 2 -- Exported decl
144 -- The second exported decl must 'get' the name 'f', so we
145 -- have to put 'f' in the avoids list before we get to the first
146 -- decl. tidyTopId then does a no-op on exported binders.
147 ; let init_env = (initTidyOccEnv avoids, emptyVarEnv)
148 avoids = [getOccName name | bndr <- typeEnvIds env_tc,
149 let name = idName bndr,
151 -- In computing our "avoids" list, we must include
153 -- all things with global names (assigned once and for
154 -- all by the renamer)
155 -- since their names are "taken".
156 -- The type environment is a convenient source of such things.
158 ; (final_env, tidy_binds)
159 <- tidyTopBinds mod nc_var ext_ids init_env binds_in
161 ; let tidy_rules = tidyIdRules final_env ext_rules
163 ; let tidy_type_env = mkFinalTypeEnv omit_iface_prags env_tc tidy_binds
165 -- Dfuns are local Ids that might have
166 -- changed their unique during tidying. Remember
167 -- to lookup the id in the TypeEnv too, because
168 -- those Ids have had their IdInfo stripped if
170 ; let (_, subst_env ) = final_env
172 case lookupVarEnv subst_env id of
173 Nothing -> dfun_panic
175 case lookupNameEnv tidy_type_env (idName id) of
179 dfun_panic = pprPanic "lookup_dfun_id" (ppr id)
181 tidy_dfun_ids = map lookup_dfun_id insts_tc
183 ; let tidy_result = mod_impl { mg_types = tidy_type_env,
184 mg_rules = tidy_rules,
185 mg_insts = tidy_dfun_ids,
186 mg_binds = tidy_binds }
188 ; endPass dflags "Tidy Core" Opt_D_dump_simpl tidy_binds
189 ; dumpIfSet_core dflags Opt_D_dump_simpl
191 (pprIdRules tidy_rules)
196 tidyCoreExpr :: CoreExpr -> IO CoreExpr
197 tidyCoreExpr expr = return (tidyExpr emptyTidyEnv expr)
201 %************************************************************************
203 \subsection{Write a new interface file}
205 %************************************************************************
208 mkFinalTypeEnv :: Bool -- Omit interface pragmas
209 -> TypeEnv -- From typechecker
210 -> [CoreBind] -- Final Ids
213 -- The competed type environment is gotten from
214 -- a) keeping the types and classes
215 -- b) removing all Ids,
216 -- c) adding Ids with correct IdInfo, including unfoldings,
217 -- gotten from the bindings
218 -- From (c) we keep only those Ids with External names;
219 -- the CoreTidy pass makes sure these are all and only
220 -- the externally-accessible ones
221 -- This truncates the type environment to include only the
222 -- exported Ids and things needed from them, which saves space
224 -- However, we do keep things like constructors, which should not appear
225 -- in interface files, because they are needed by importing modules when
226 -- using the compilation manager
228 mkFinalTypeEnv omit_iface_prags type_env tidy_binds
229 = extendTypeEnvList (filterNameEnv keep_it type_env) final_ids
231 final_ids = [ AnId (strip_id_info id)
232 | bind <- tidy_binds,
233 id <- bindersOf bind,
234 isExternalName (idName id)]
237 | omit_iface_prags = id `setIdInfo` vanillaIdInfo
239 -- If the interface file has no pragma info then discard all
242 -- This is not so important for *this* module, but it's
243 -- vital for ghc --make:
244 -- subsequent compilations must not see (e.g.) the arity if
245 -- the interface file does not contain arity
246 -- If they do, they'll exploit the arity; then the arity might
247 -- change, but the iface file doesn't change => recompilation
248 -- does not happen => disaster
250 -- This IdInfo will live long-term in the Id => vanillaIdInfo makes
251 -- a conservative assumption about Caf-hood
253 -- We're not worried about occurrences of these Ids in unfoldings,
254 -- because in OmitInterfacePragmas mode we're stripping all the
255 -- unfoldings anyway.
257 -- We keep implicit Ids, because they won't appear
258 -- in the bindings from which final_ids are derived!
259 keep_it (AnId id) = isImplicitId id -- Remove all Ids except implicit ones
260 keep_it other = True -- Keep all TyCons and Classes
264 findExternalRules :: Bool -- Omit interface pragmas
266 -> [IdCoreRule] -- Orphan rules
267 -> IdEnv a -- Ids that are exported, so we need their rules
269 -- The complete rules are gotten by combining
270 -- a) the orphan rules
271 -- b) rules embedded in the top-level Ids
272 findExternalRules omit_iface_prags binds orphan_rules ext_ids
273 | omit_iface_prags = []
275 = filter needed_rule (orphan_rules ++ local_rules)
278 | id <- bindersOfBinds binds,
279 id `elemVarEnv` ext_ids,
280 rule <- idCoreRules id
282 needed_rule (id, rule)
283 = not (isBuiltinRule rule)
284 -- We can't print builtin rules in interface files
285 -- Since they are built in, an importing module
286 -- will have access to them anyway
288 && not (any internal_id (varSetElems (ruleLhsFreeIds rule)))
289 -- Don't export a rule whose LHS mentions an Id that
290 -- is completely internal (i.e. not visible to an
293 internal_id id = isLocalId id && not (id `elemVarEnv` ext_ids)
296 %************************************************************************
298 \subsection{Step 1: finding externals}
300 %************************************************************************
303 findExternalSet :: Bool -- omit interface pragmas
304 -> [CoreBind] -> [IdCoreRule]
305 -> IdEnv Bool -- In domain => external
306 -- Range = True <=> show unfolding
307 -- Step 1 from the notes above
308 findExternalSet omit_iface_prags binds orphan_rules
309 = foldr find init_needed binds
311 orphan_rule_ids :: IdSet
312 orphan_rule_ids = unionVarSets [ ruleRhsFreeVars rule
313 | (_, rule) <- orphan_rules]
314 init_needed :: IdEnv Bool
315 init_needed = mapUFM (\_ -> False) orphan_rule_ids
316 -- The mapUFM is a bit cheesy. It is a cheap way
317 -- to turn the set of orphan_rule_ids, which we use to initialise
318 -- the sweep, into a mapping saying 'don't expose unfolding'
319 -- (When we come to the binding site we may change our mind, of course.)
321 find (NonRec id rhs) needed
322 | need_id needed id = addExternal omit_iface_prags (id,rhs) needed
324 find (Rec prs) needed = find_prs prs needed
326 -- For a recursive group we have to look for a fixed point
328 | null needed_prs = needed
329 | otherwise = find_prs other_prs new_needed
331 (needed_prs, other_prs) = partition (need_pr needed) prs
332 new_needed = foldr (addExternal omit_iface_prags) needed needed_prs
334 -- The 'needed' set contains the Ids that are needed by earlier
335 -- interface file emissions. If the Id isn't in this set, and isn't
336 -- exported, there's no need to emit anything
337 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
338 need_pr needed_set (id,rhs) = need_id needed_set id
340 addExternal :: Bool -> (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
341 -- The Id is needed; extend the needed set
342 -- with it and its dependents (free vars etc)
343 addExternal omit_iface_prags (id,rhs) needed
344 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
347 add_occ id needed = extendVarEnv needed id False
348 -- "False" because we don't know we need the Id's unfolding
349 -- We'll override it later when we find the binding site
351 new_needed_ids | omit_iface_prags = emptyVarSet
352 | otherwise = worker_ids `unionVarSet`
353 unfold_ids `unionVarSet`
357 dont_inline = isNeverActive (inlinePragInfo idinfo)
358 loop_breaker = isLoopBreaker (occInfo idinfo)
359 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
360 spec_ids = rulesRhsFreeVars (specInfo idinfo)
361 worker_info = workerInfo idinfo
363 -- Stuff to do with the Id's unfolding
364 -- The simplifier has put an up-to-date unfolding
365 -- in the IdInfo, but the RHS will do just as well
366 unfolding = unfoldingInfo idinfo
367 rhs_is_small = not (neverUnfold unfolding)
369 -- We leave the unfolding there even if there is a worker
370 -- In GHCI the unfolding is used by importers
371 -- When writing an interface file, we omit the unfolding
372 -- if there is a worker
373 show_unfold = not bottoming_fn && -- Not necessary
376 rhs_is_small -- Small enough
378 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
379 | otherwise = emptyVarSet
381 worker_ids = case worker_info of
382 HasWorker work_id _ -> unitVarSet work_id
383 otherwise -> emptyVarSet
387 %************************************************************************
389 \subsection{Step 2: top-level tidying}
391 %************************************************************************
395 -- TopTidyEnv: when tidying we need to know
396 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
397 -- These may have arisen because the
398 -- renamer read in an interface file mentioning M.$wf, say,
399 -- and assigned it unique r77. If, on this compilation, we've
400 -- invented an Id whose name is $wf (but with a different unique)
401 -- we want to rename it to have unique r77, so that we can do easy
402 -- comparisons with stuff from the interface file
404 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
407 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
409 tidyTopBinds :: Module
410 -> IORef NameCache -- For allocating new unique names
411 -> IdEnv Bool -- Domain = Ids that should be external
412 -- True <=> their unfolding is external too
413 -> TidyEnv -> [CoreBind]
414 -> IO (TidyEnv, [CoreBind])
415 tidyTopBinds mod nc_var ext_ids tidy_env []
416 = return (tidy_env, [])
418 tidyTopBinds mod nc_var ext_ids tidy_env (b:bs)
419 = do { (tidy_env1, b') <- tidyTopBind mod nc_var ext_ids tidy_env b
420 ; (tidy_env2, bs') <- tidyTopBinds mod nc_var ext_ids tidy_env1 bs
421 ; return (tidy_env2, b':bs') }
423 ------------------------
424 tidyTopBind :: Module
425 -> IORef NameCache -- For allocating new unique names
426 -> IdEnv Bool -- Domain = Ids that should be external
427 -- True <=> their unfolding is external too
428 -> TidyEnv -> CoreBind
429 -> IO (TidyEnv, CoreBind)
431 tidyTopBind mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (NonRec bndr rhs)
432 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
433 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
434 ; subst2 = extendVarEnv subst1 bndr bndr'
435 ; tidy_env2 = (occ_env2, subst2) }
436 ; return (tidy_env2, NonRec bndr' rhs') }
438 caf_info = hasCafRefs subst1 (idArity bndr) rhs
440 tidyTopBind mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (Rec prs)
441 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
442 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
444 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
445 ; tidy_env2 = (occ_env2, subst2) }
446 ; return (tidy_env2, Rec prs') }
450 -- the CafInfo for a recursive group says whether *any* rhs in
451 -- the group may refer indirectly to a CAF (because then, they all do).
453 | or [ mayHaveCafRefs (hasCafRefs subst1 (idArity bndr) rhs)
454 | (bndr,rhs) <- prs ] = MayHaveCafRefs
455 | otherwise = NoCafRefs
457 --------------------------------------------------------------------
459 -- This is where we set names to local/global based on whether they really are
460 -- externally visible (see comment at the top of this module). If the name
461 -- was previously local, we have to give it a unique occurrence name if
462 -- we intend to externalise it.
463 tidyTopNames mod nc_var ext_ids occ_env [] = return (occ_env, [])
464 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
465 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
466 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
467 ; return (occ_env2, name:names) }
469 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
470 -> Id -> IO (TidyOccEnv, Name)
471 tidyTopName mod nc_var ext_ids occ_env id
472 | global && internal = return (occ_env, localiseName name)
474 | global && external = return (occ_env, name)
475 -- Global names are assumed to have been allocated by the renamer,
476 -- so they already have the "right" unique
477 -- And it's a system-wide unique too
479 -- Now we get to the real reason that all this is in the IO Monad:
480 -- we have to update the name cache in a nice atomic fashion
482 | local && internal = do { nc <- readIORef nc_var
483 ; let (nc', new_local_name) = mk_new_local nc
484 ; writeIORef nc_var nc'
485 ; return (occ_env', new_local_name) }
486 -- Even local, internal names must get a unique occurrence, because
487 -- if we do -split-objs we externalise the name later, in the code generator
489 -- Similarly, we must make sure it has a system-wide Unique, because
490 -- the byte-code generator builds a system-wide Name->BCO symbol table
492 | local && external = do { nc <- readIORef nc_var
493 ; let (nc', new_external_name) = mk_new_external nc
494 ; writeIORef nc_var nc'
495 ; return (occ_env', new_external_name) }
498 external = id `elemVarEnv` ext_ids
499 global = isExternalName name
501 internal = not external
502 mb_parent = nameParent_maybe name
503 loc = nameSrcLoc name
505 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
507 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
509 (us1, us2) = splitUniqSupply (nsUniqs nc)
510 uniq = uniqFromSupply us1
512 mk_new_external nc = allocateGlobalBinder nc mod occ' mb_parent loc
513 -- If we want to externalise a currently-local name, check
514 -- whether we have already assigned a unique for it.
515 -- If so, use it; if not, extend the table.
516 -- All this is done by allcoateGlobalBinder.
517 -- This is needed when *re*-compiling a module in GHCi; we want to
518 -- use the same name for externally-visible things as we did before.
521 -----------------------------------------------------------
522 tidyTopPair :: VarEnv Bool
523 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
524 -- It is knot-tied: don't look at it!
527 -> (Id, CoreExpr) -- Binder and RHS before tidying
529 -- This function is the heart of Step 2
530 -- The rec_tidy_env is the one to use for the IdInfo
531 -- It's necessary because when we are dealing with a recursive
532 -- group, a variable late in the group might be mentioned
533 -- in the IdInfo of one early in the group
535 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
536 = ASSERT(isLocalId bndr) -- "all Ids defined in this module are local
537 -- until the CoreTidy phase" --GHC comentary
540 bndr' = mkVanillaGlobal name' ty' idinfo'
541 ty' = tidyTopType (idType bndr)
542 rhs' = tidyExpr rhs_tidy_env rhs
543 idinfo' = tidyTopIdInfo rhs_tidy_env (isJust maybe_external)
544 (idInfo bndr) unfold_info arity
547 -- Expose an unfolding if ext_ids tells us to
548 -- Remember that ext_ids maps an Id to a Bool:
549 -- True to show the unfolding, False to hide it
550 maybe_external = lookupVarEnv ext_ids bndr
551 show_unfold = maybe_external `orElse` False
552 unfold_info | show_unfold = mkTopUnfolding rhs'
553 | otherwise = noUnfolding
555 -- Usually the Id will have an accurate arity on it, because
556 -- the simplifier has just run, but not always.
557 -- One case I found was when the last thing the simplifier
558 -- did was to let-bind a non-atomic argument and then float
559 -- it to the top level. So it seems more robust just to
561 arity = exprArity rhs
564 -- tidyTopIdInfo creates the final IdInfo for top-level
565 -- binders. There are two delicate pieces:
567 -- * Arity. After CoreTidy, this arity must not change any more.
568 -- Indeed, CorePrep must eta expand where necessary to make
569 -- the manifest arity equal to the claimed arity.
571 -- * CAF info. This must also remain valid through to code generation.
572 -- We add the info here so that it propagates to all
573 -- occurrences of the binders in RHSs, and hence to occurrences in
574 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
575 -- CoreToStg makes use of this when constructing SRTs.
577 tidyTopIdInfo tidy_env is_external idinfo unfold_info arity caf_info
578 | not is_external -- For internal Ids (not externally visible)
579 = vanillaIdInfo -- we only need enough info for code generation
580 -- Arity and strictness info are enough;
581 -- c.f. CoreTidy.tidyLetBndr
582 `setCafInfo` caf_info
584 `setAllStrictnessInfo` newStrictnessInfo idinfo
586 | otherwise -- Externally-visible Ids get the whole lot
588 `setCafInfo` caf_info
590 `setAllStrictnessInfo` newStrictnessInfo idinfo
591 `setInlinePragInfo` inlinePragInfo idinfo
592 `setUnfoldingInfo` unfold_info
593 `setWorkerInfo` tidyWorker tidy_env (workerInfo idinfo)
594 -- NB: we throw away the Rules
595 -- They have already been extracted by findExternalRules
599 ------------ Worker --------------
600 tidyWorker tidy_env (HasWorker work_id wrap_arity)
601 = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
602 tidyWorker tidy_env other
606 %************************************************************************
608 \subsection{Figuring out CafInfo for an expression}
610 %************************************************************************
612 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
613 We mark such things as `MayHaveCafRefs' because this information is
614 used to decide whether a particular closure needs to be referenced
617 There are two reasons for setting MayHaveCafRefs:
618 a) The RHS is a CAF: a top-level updatable thunk.
619 b) The RHS refers to something that MayHaveCafRefs
621 Possible improvement: In an effort to keep the number of CAFs (and
622 hence the size of the SRTs) down, we could also look at the expression and
623 decide whether it requires a small bounded amount of heap, so we can ignore
624 it as a CAF. In these cases however, we would need to use an additional
625 CAF list to keep track of non-collectable CAFs.
628 hasCafRefs :: VarEnv Var -> Arity -> CoreExpr -> CafInfo
629 hasCafRefs p arity expr
630 | is_caf || mentions_cafs = MayHaveCafRefs
631 | otherwise = NoCafRefs
633 mentions_cafs = isFastTrue (cafRefs p expr)
634 is_caf = not (arity > 0 || rhsIsStatic expr)
635 -- NB. we pass in the arity of the expression, which is expected
636 -- to be calculated by exprArity. This is because exprArity
637 -- knows how much eta expansion is going to be done by
638 -- CorePrep later on, and we don't want to duplicate that
639 -- knowledge in rhsIsStatic below.
642 -- imported Ids first:
643 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
644 -- now Ids local to this module:
646 case lookupVarEnv p id of
647 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
648 Nothing -> fastBool False
650 cafRefs p (Lit l) = fastBool False
651 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
652 cafRefs p (Lam x e) = cafRefs p e
653 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
654 cafRefs p (Case e bndr alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
655 cafRefs p (Note n e) = cafRefs p e
656 cafRefs p (Type t) = fastBool False
658 cafRefss p [] = fastBool False
659 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
661 -- hack for lazy-or over FastBool.
662 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))