2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section{Tidying up Core}
7 module TidyPgm( mkBootModDetails, tidyProgram ) where
9 #include "HsVersions.h"
11 import DynFlags ( DynFlag(..), dopt )
12 import Packages ( HomeModules )
14 import CoreUnfold ( noUnfolding, mkTopUnfolding )
15 import CoreFVs ( ruleLhsFreeIds, exprSomeFreeVars )
16 import CoreTidy ( tidyExpr, tidyVarOcc, tidyRules )
17 import PprCore ( pprRules )
18 import CoreLint ( showPass, endPass )
19 import CoreUtils ( exprArity, rhsIsStatic )
22 import Var ( Id, Var )
23 import Id ( idType, idInfo, idName, idCoreRules, isGlobalId,
24 isExportedId, mkVanillaGlobal, isLocalId, isNaughtyRecordSelector,
25 idArity, idCafInfo, idUnfolding, isImplicitId, setIdInfo
27 import IdInfo {- loads of stuff -}
28 import InstEnv ( Instance, DFunId, instanceDFunId, setInstanceDFunId )
29 import NewDemand ( isBottomingSig, topSig )
30 import BasicTypes ( Arity, isNeverActive )
31 import Name ( Name, getOccName, nameOccName, mkInternalName,
32 localiseName, isExternalName, nameSrcLoc, nameParent_maybe,
33 isWiredInName, getName
35 import NameSet ( NameSet, elemNameSet )
36 import IfaceEnv ( allocateGlobalBinder )
37 import NameEnv ( filterNameEnv, mapNameEnv )
38 import OccName ( TidyOccEnv, initTidyOccEnv, tidyOccName )
39 import Type ( tidyTopType )
40 import TcType ( isFFITy )
41 import DataCon ( dataConName, dataConFieldLabels, dataConWrapId_maybe )
42 import TyCon ( TyCon, makeTyConAbstract, tyConDataCons, isNewTyCon,
43 newTyConRep, tyConSelIds, isAlgTyCon, isEnumerationTyCon )
44 import Class ( classSelIds )
45 import Module ( Module )
46 import HscTypes ( HscEnv(..), NameCache( nsUniqs ), CgGuts(..),
47 TypeEnv, typeEnvIds, typeEnvElts, typeEnvTyCons,
48 extendTypeEnvWithIds, lookupTypeEnv,
49 ModGuts(..), TyThing(..), ModDetails(..), Dependencies(..)
51 import Maybes ( orElse, mapCatMaybes )
52 import ErrUtils ( showPass, dumpIfSet_core )
53 import UniqSupply ( splitUniqSupply, uniqFromSupply )
54 import List ( partition )
55 import Maybe ( isJust )
57 import DATA_IOREF ( IORef, readIORef, writeIORef )
58 import FastTypes hiding ( fastOr )
62 Constructing the TypeEnv, Instances, Rules from which the ModIface is
63 constructed, and which goes on to subsequent modules in --make mode.
65 Most of the interface file is obtained simply by serialising the
66 TypeEnv. One important consequence is that if the *interface file*
67 has pragma info if and only if the final TypeEnv does. This is not so
68 important for *this* module, but it's essential for ghc --make:
69 subsequent compilations must not see (e.g.) the arity if the interface
70 file does not contain arity If they do, they'll exploit the arity;
71 then the arity might change, but the iface file doesn't change =>
72 recompilation does not happen => disaster.
74 For data types, the final TypeEnv will have a TyThing for the TyCon,
75 plus one for each DataCon; the interface file will contain just one
76 data type declaration, but it is de-serialised back into a collection
79 %************************************************************************
83 %************************************************************************
86 Plan A: mkBootModDetails: omit pragmas, make interfaces small
87 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
90 * Drop all WiredIn things from the TypeEnv
91 (we never want them in interface files)
93 * Retain all TyCons and Classes in the TypeEnv, to avoid
94 having to find which ones are mentioned in the
97 * Trim off the constructors of non-exported TyCons, both
98 from the TyCon and from the TypeEnv
100 * Drop non-exported Ids from the TypeEnv
102 * Tidy the types of the DFunIds of Instances,
103 make them into GlobalIds, (they already have External Names)
104 and add them to the TypeEnv
106 * Tidy the types of the (exported) Ids in the TypeEnv,
107 make them into GlobalIds (they already have External Names)
109 * Drop rules altogether
111 * Tidy the bindings, to ensure that the Caf and Arity
112 information is correct for each top-level binder; the
113 code generator needs it. And to ensure that local names have
114 distinct OccNames in case of object-file splitting
117 mkBootModDetails :: HscEnv -> ModGuts -> IO ModDetails
118 -- This is Plan A: make a small type env when typechecking only,
119 -- or when compiling a hs-boot file, or simply when not using -O
121 -- We don't look at the bindings at all -- there aren't any
124 mkBootModDetails hsc_env (ModGuts { mg_module = mod,
125 mg_exports = exports,
128 = do { let dflags = hsc_dflags hsc_env
129 ; showPass dflags "Tidy [hoot] type env"
131 ; let { ispecs' = tidyInstances tidyExternalId ispecs
132 ; type_env1 = filterNameEnv (not . isWiredInThing) type_env
133 ; type_env2 = mapNameEnv tidyBootThing type_env1
134 ; type_env' = extendTypeEnvWithIds type_env2
135 (map instanceDFunId ispecs')
137 ; return (ModDetails { md_types = type_env',
140 md_exports = exports })
144 isWiredInThing :: TyThing -> Bool
145 isWiredInThing thing = isWiredInName (getName thing)
147 tidyBootThing :: TyThing -> TyThing
148 -- Just externalise the Ids; keep everything
149 tidyBootThing (AnId id) | isLocalId id = AnId (tidyExternalId id)
150 tidyBootThing thing = thing
152 tidyExternalId :: Id -> Id
153 -- Takes an LocalId with an External Name,
154 -- makes it into a GlobalId with VanillaIdInfo, and tidies its type
155 -- (NB: vanillaIdInfo makes a conservative assumption about Caf-hood.)
157 = ASSERT2( isLocalId id && isExternalName (idName id), ppr id )
158 mkVanillaGlobal (idName id) (tidyTopType (idType id)) vanillaIdInfo
162 %************************************************************************
164 Plan B: tidy bindings, make TypeEnv full of IdInfo
166 %************************************************************************
168 Plan B: include pragmas, make interfaces
169 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
170 * Figure out which Ids are externally visible
172 * Tidy the bindings, externalising appropriate Ids
174 * Drop all Ids from the TypeEnv, and add all the External Ids from
175 the bindings. (This adds their IdInfo to the TypeEnv; and adds
176 floated-out Ids that weren't even in the TypeEnv before.)
178 Step 1: Figure out external Ids
179 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
180 First we figure out which Ids are "external" Ids. An
181 "external" Id is one that is visible from outside the compilation
183 a) the user exported ones
184 b) ones mentioned in the unfoldings, workers,
185 or rules of externally-visible ones
186 This exercise takes a sweep of the bindings bottom to top. Actually,
187 in Step 2 we're also going to need to know which Ids should be
188 exported with their unfoldings, so we produce not an IdSet but an
192 Step 2: Tidy the program
193 ~~~~~~~~~~~~~~~~~~~~~~~~
194 Next we traverse the bindings top to bottom. For each *top-level*
197 1. Make it into a GlobalId; its IdDetails becomes VanillaGlobal,
198 reflecting the fact that from now on we regard it as a global,
201 2. Give it a system-wide Unique.
202 [Even non-exported things need system-wide Uniques because the
203 byte-code generator builds a single Name->BCO symbol table.]
205 We use the NameCache kept in the HscEnv as the
206 source of such system-wide uniques.
208 For external Ids, use the original-name cache in the NameCache
209 to ensure that the unique assigned is the same as the Id had
210 in any previous compilation run.
212 3. If it's an external Id, make it have a External Name, otherwise
213 make it have an Internal Name.
214 This is used by the code generator to decide whether
215 to make the label externally visible
217 4. Give external Ids a "tidy" OccName. This means
218 we can print them in interface files without confusing
219 "x" (unique 5) with "x" (unique 10).
221 5. Give it its UTTERLY FINAL IdInfo; in ptic,
222 * its unfolding, if it should have one
224 * its arity, computed from the number of visible lambdas
226 * its CAF info, computed from what is free in its RHS
229 Finally, substitute these new top-level binders consistently
230 throughout, including in unfoldings. We also tidy binders in
231 RHSs, so that they print nicely in interfaces.
234 tidyProgram :: HscEnv -> ModGuts -> IO (CgGuts, ModDetails)
236 mod_impl@(ModGuts { mg_module = mod, mg_exports = exports,
237 mg_types = type_env, mg_insts = insts_tc,
239 mg_rules = imp_rules,
240 mg_dir_imps = dir_imps, mg_deps = deps,
241 mg_home_mods = home_mods,
242 mg_foreign = foreign_stubs })
244 = do { let dflags = hsc_dflags hsc_env
245 ; showPass dflags "Tidy Core"
247 ; let { omit_prags = dopt Opt_OmitInterfacePragmas dflags
248 ; ext_ids = findExternalIds omit_prags binds
251 | otherwise = findExternalRules binds imp_rules ext_ids
252 -- findExternalRules filters imp_rules to avoid binders that
253 -- aren't externally visible; but the externally-visible binders
254 -- are computed (by findExternalIds) assuming that all orphan
255 -- rules are exported (they get their Exported flag set in the desugarer)
256 -- So in fact we may export more than we need.
257 -- (It's a sort of mutual recursion.)
260 ; (tidy_env, tidy_binds) <- tidyTopBinds hsc_env home_mods mod type_env ext_ids binds
262 ; let { tidy_type_env = tidyTypeEnv omit_prags exports type_env tidy_binds
263 ; tidy_ispecs = tidyInstances (lookup_dfun tidy_type_env) insts_tc
264 -- A DFunId will have a binding in tidy_binds, and so
265 -- will now be in final_env, replete with IdInfo
266 -- Its name will be unchanged since it was born, but
267 -- we want Global, IdInfo-rich (or not) DFunId in the tidy_ispecs
269 ; tidy_rules = tidyRules tidy_env ext_rules
270 -- You might worry that the tidy_env contains IdInfo-rich stuff
271 -- and indeed it does, but if omit_prags is on, ext_rules is empty
273 ; implicit_binds = getImplicitBinds type_env
274 ; all_tidy_binds = implicit_binds ++ tidy_binds
275 ; alg_tycons = filter isAlgTyCon (typeEnvTyCons type_env)
278 ; endPass dflags "Tidy Core" Opt_D_dump_simpl all_tidy_binds
279 ; dumpIfSet_core dflags Opt_D_dump_simpl
281 (pprRules tidy_rules)
283 ; return (CgGuts { cg_module = mod,
284 cg_tycons = alg_tycons,
285 cg_binds = all_tidy_binds,
286 cg_dir_imps = dir_imps,
287 cg_foreign = foreign_stubs,
288 cg_home_mods = home_mods,
289 cg_dep_pkgs = dep_pkgs deps },
291 ModDetails { md_types = tidy_type_env,
292 md_rules = tidy_rules,
293 md_insts = tidy_ispecs,
294 md_exports = exports })
297 lookup_dfun type_env dfun_id
298 = case lookupTypeEnv type_env (idName dfun_id) of
299 Just (AnId dfun_id') -> dfun_id'
300 other -> pprPanic "lookup_dfun" (ppr dfun_id)
302 tidyTypeEnv :: Bool -> NameSet -> TypeEnv -> [CoreBind] -> TypeEnv
304 -- The competed type environment is gotten from
305 -- Dropping any wired-in things, and then
306 -- a) keeping the types and classes
307 -- b) removing all Ids,
308 -- c) adding Ids with correct IdInfo, including unfoldings,
309 -- gotten from the bindings
310 -- From (c) we keep only those Ids with External names;
311 -- the CoreTidy pass makes sure these are all and only
312 -- the externally-accessible ones
313 -- This truncates the type environment to include only the
314 -- exported Ids and things needed from them, which saves space
316 tidyTypeEnv omit_prags exports type_env tidy_binds
317 = let type_env1 = filterNameEnv keep_it type_env
318 type_env2 = extendTypeEnvWithIds type_env1 final_ids
319 type_env3 | omit_prags = mapNameEnv trim_thing type_env2
320 | otherwise = type_env2
324 final_ids = [ id | id <- bindersOfBinds tidy_binds,
325 isExternalName (idName id)]
327 -- We keep GlobalIds, because they won't appear
328 -- in the bindings from which final_ids are derived!
329 -- (The bindings bind LocalIds.)
330 keep_it thing | isWiredInThing thing = False
331 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
332 keep_it other = True -- Keep all TyCons, DataCons, and Classes
336 ATyCon tc | mustExposeTyCon exports tc -> thing
337 | otherwise -> ATyCon (makeTyConAbstract tc)
339 AnId id | isImplicitId id -> thing
340 | otherwise -> AnId (id `setIdInfo` vanillaIdInfo)
344 mustExposeTyCon :: NameSet -- Exports
345 -> TyCon -- The tycon
346 -> Bool -- Can its rep be hidden?
347 -- We are compiling without -O, and thus trying to write as little as
348 -- possible into the interface file. But we must expose the details of
349 -- any data types whose constructors or fields are exported
350 mustExposeTyCon exports tc
351 | not (isAlgTyCon tc) -- Synonyms
353 | isEnumerationTyCon tc -- For an enumeration, exposing the constructors
354 = True -- won't lead to the need for further exposure
355 -- (This includes data types with no constructors.)
356 | otherwise -- Newtype, datatype
357 = any exported_con (tyConDataCons tc)
358 -- Expose rep if any datacon or field is exported
360 || (isNewTyCon tc && isFFITy (snd (newTyConRep tc)))
361 -- Expose the rep for newtypes if the rep is an FFI type.
362 -- For a very annoying reason. 'Foreign import' is meant to
363 -- be able to look through newtypes transparently, but it
364 -- can only do that if it can "see" the newtype representation
366 exported_con con = any (`elemNameSet` exports)
367 (dataConName con : dataConFieldLabels con)
369 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
370 tidyInstances tidy_dfun ispecs
373 tidy ispec = setInstanceDFunId ispec $
374 tidy_dfun (instanceDFunId ispec)
376 getImplicitBinds :: TypeEnv -> [CoreBind]
377 getImplicitBinds type_env
378 = map get_defn (concatMap implicit_con_ids (typeEnvTyCons type_env)
379 ++ concatMap other_implicit_ids (typeEnvElts type_env))
380 -- Put the constructor wrappers first, because
381 -- other implicit bindings (notably the fromT functions arising
382 -- from generics) use the constructor wrappers. At least that's
383 -- what External Core likes
385 implicit_con_ids tc = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
387 other_implicit_ids (ATyCon tc) = filter (not . isNaughtyRecordSelector) (tyConSelIds tc)
388 -- The "naughty" ones are not real functions at all
389 -- They are there just so we can get decent error messages
390 -- See Note [Naughty record selectors] in MkId.lhs
391 other_implicit_ids (AClass cl) = classSelIds cl
392 other_implicit_ids other = []
394 get_defn :: Id -> CoreBind
395 get_defn id = NonRec id (tidyExpr emptyTidyEnv rhs)
397 rhs = unfoldingTemplate (idUnfolding id)
398 -- Don't forget to tidy the body ! Otherwise you get silly things like
399 -- \ tpl -> case tpl of tpl -> (tpl,tpl) -> tpl
403 %************************************************************************
405 \subsection{Step 1: finding externals}
407 %************************************************************************
410 findExternalIds :: Bool
412 -> IdEnv Bool -- In domain => external
413 -- Range = True <=> show unfolding
414 -- Step 1 from the notes above
415 findExternalIds omit_prags binds
417 = mkVarEnv [ (id,False) | id <- bindersOfBinds binds, isExportedId id ]
420 = foldr find emptyVarEnv binds
422 find (NonRec id rhs) needed
423 | need_id needed id = addExternal (id,rhs) needed
425 find (Rec prs) needed = find_prs prs needed
427 -- For a recursive group we have to look for a fixed point
429 | null needed_prs = needed
430 | otherwise = find_prs other_prs new_needed
432 (needed_prs, other_prs) = partition (need_pr needed) prs
433 new_needed = foldr addExternal needed needed_prs
435 -- The 'needed' set contains the Ids that are needed by earlier
436 -- interface file emissions. If the Id isn't in this set, and isn't
437 -- exported, there's no need to emit anything
438 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
439 need_pr needed_set (id,rhs) = need_id needed_set id
441 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
442 -- The Id is needed; extend the needed set
443 -- with it and its dependents (free vars etc)
444 addExternal (id,rhs) needed
445 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
448 add_occ id needed = extendVarEnv needed id False
449 -- "False" because we don't know we need the Id's unfolding
450 -- We'll override it later when we find the binding site
452 new_needed_ids = worker_ids `unionVarSet`
453 unfold_ids `unionVarSet`
457 dont_inline = isNeverActive (inlinePragInfo idinfo)
458 loop_breaker = isLoopBreaker (occInfo idinfo)
459 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
460 spec_ids = specInfoFreeVars (specInfo idinfo)
461 worker_info = workerInfo idinfo
463 -- Stuff to do with the Id's unfolding
464 -- The simplifier has put an up-to-date unfolding
465 -- in the IdInfo, but the RHS will do just as well
466 unfolding = unfoldingInfo idinfo
467 rhs_is_small = not (neverUnfold unfolding)
469 -- We leave the unfolding there even if there is a worker
470 -- In GHCI the unfolding is used by importers
471 -- When writing an interface file, we omit the unfolding
472 -- if there is a worker
473 show_unfold = not bottoming_fn && -- Not necessary
476 rhs_is_small -- Small enough
478 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
479 | otherwise = emptyVarSet
481 worker_ids = case worker_info of
482 HasWorker work_id _ -> unitVarSet work_id
483 otherwise -> emptyVarSet
488 findExternalRules :: [CoreBind]
489 -> [CoreRule] -- Non-local rules (i.e. ones for imported fns)
490 -> IdEnv a -- Ids that are exported, so we need their rules
492 -- The complete rules are gotten by combining
493 -- a) the non-local rules
494 -- b) rules embedded in the top-level Ids
495 findExternalRules binds non_local_rules ext_ids
496 = filter (not . internal_rule) (non_local_rules ++ local_rules)
499 | id <- bindersOfBinds binds,
500 id `elemVarEnv` ext_ids,
501 rule <- idCoreRules id
505 = any internal_id (varSetElems (ruleLhsFreeIds rule))
506 -- Don't export a rule whose LHS mentions a locally-defined
507 -- Id that is completely internal (i.e. not visible to an
510 internal_id id = not (id `elemVarEnv` ext_ids)
515 %************************************************************************
517 \subsection{Step 2: top-level tidying}
519 %************************************************************************
523 -- TopTidyEnv: when tidying we need to know
524 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
525 -- These may have arisen because the
526 -- renamer read in an interface file mentioning M.$wf, say,
527 -- and assigned it unique r77. If, on this compilation, we've
528 -- invented an Id whose name is $wf (but with a different unique)
529 -- we want to rename it to have unique r77, so that we can do easy
530 -- comparisons with stuff from the interface file
532 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
535 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
537 tidyTopBinds :: HscEnv
541 -> IdEnv Bool -- Domain = Ids that should be external
542 -- True <=> their unfolding is external too
544 -> IO (TidyEnv, [CoreBind])
546 tidyTopBinds hsc_env hmods mod type_env ext_ids binds
547 = tidy init_env binds
549 nc_var = hsc_NC hsc_env
551 -- We also make sure to avoid any exported binders. Consider
552 -- f{-u1-} = 1 -- Local decl
554 -- f{-u2-} = 2 -- Exported decl
556 -- The second exported decl must 'get' the name 'f', so we
557 -- have to put 'f' in the avoids list before we get to the first
558 -- decl. tidyTopId then does a no-op on exported binders.
559 init_env = (initTidyOccEnv avoids, emptyVarEnv)
560 avoids = [getOccName name | bndr <- typeEnvIds type_env,
561 let name = idName bndr,
563 -- In computing our "avoids" list, we must include
565 -- all things with global names (assigned once and for
566 -- all by the renamer)
567 -- since their names are "taken".
568 -- The type environment is a convenient source of such things.
570 tidy env [] = return (env, [])
571 tidy env (b:bs) = do { (env1, b') <- tidyTopBind hmods mod nc_var ext_ids env b
572 ; (env2, bs') <- tidy env1 bs
573 ; return (env2, b':bs') }
575 ------------------------
576 tidyTopBind :: HomeModules
578 -> IORef NameCache -- For allocating new unique names
579 -> IdEnv Bool -- Domain = Ids that should be external
580 -- True <=> their unfolding is external too
581 -> TidyEnv -> CoreBind
582 -> IO (TidyEnv, CoreBind)
584 tidyTopBind hmods mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (NonRec bndr rhs)
585 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
586 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
587 ; subst2 = extendVarEnv subst1 bndr bndr'
588 ; tidy_env2 = (occ_env2, subst2) }
589 ; return (tidy_env2, NonRec bndr' rhs') }
591 caf_info = hasCafRefs hmods subst1 (idArity bndr) rhs
593 tidyTopBind hmods mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (Rec prs)
594 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
595 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
597 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
598 ; tidy_env2 = (occ_env2, subst2) }
599 ; return (tidy_env2, Rec prs') }
603 -- the CafInfo for a recursive group says whether *any* rhs in
604 -- the group may refer indirectly to a CAF (because then, they all do).
606 | or [ mayHaveCafRefs (hasCafRefs hmods subst1 (idArity bndr) rhs)
607 | (bndr,rhs) <- prs ] = MayHaveCafRefs
608 | otherwise = NoCafRefs
610 --------------------------------------------------------------------
612 -- This is where we set names to local/global based on whether they really are
613 -- externally visible (see comment at the top of this module). If the name
614 -- was previously local, we have to give it a unique occurrence name if
615 -- we intend to externalise it.
616 tidyTopNames mod nc_var ext_ids occ_env [] = return (occ_env, [])
617 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
618 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
619 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
620 ; return (occ_env2, name:names) }
622 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
623 -> Id -> IO (TidyOccEnv, Name)
624 tidyTopName mod nc_var ext_ids occ_env id
625 | global && internal = return (occ_env, localiseName name)
627 | global && external = return (occ_env, name)
628 -- Global names are assumed to have been allocated by the renamer,
629 -- so they already have the "right" unique
630 -- And it's a system-wide unique too
632 -- Now we get to the real reason that all this is in the IO Monad:
633 -- we have to update the name cache in a nice atomic fashion
635 | local && internal = do { nc <- readIORef nc_var
636 ; let (nc', new_local_name) = mk_new_local nc
637 ; writeIORef nc_var nc'
638 ; return (occ_env', new_local_name) }
639 -- Even local, internal names must get a unique occurrence, because
640 -- if we do -split-objs we externalise the name later, in the code generator
642 -- Similarly, we must make sure it has a system-wide Unique, because
643 -- the byte-code generator builds a system-wide Name->BCO symbol table
645 | local && external = do { nc <- readIORef nc_var
646 ; let (nc', new_external_name) = mk_new_external nc
647 ; writeIORef nc_var nc'
648 ; return (occ_env', new_external_name) }
651 external = id `elemVarEnv` ext_ids
652 global = isExternalName name
654 internal = not external
655 mb_parent = nameParent_maybe name
656 loc = nameSrcLoc name
658 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
660 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
662 (us1, us2) = splitUniqSupply (nsUniqs nc)
663 uniq = uniqFromSupply us1
665 mk_new_external nc = allocateGlobalBinder nc mod occ' mb_parent loc
666 -- If we want to externalise a currently-local name, check
667 -- whether we have already assigned a unique for it.
668 -- If so, use it; if not, extend the table.
669 -- All this is done by allcoateGlobalBinder.
670 -- This is needed when *re*-compiling a module in GHCi; we must
671 -- use the same name for externally-visible things as we did before.
674 -----------------------------------------------------------
675 tidyTopPair :: VarEnv Bool
676 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
677 -- It is knot-tied: don't look at it!
680 -> (Id, CoreExpr) -- Binder and RHS before tidying
682 -- This function is the heart of Step 2
683 -- The rec_tidy_env is the one to use for the IdInfo
684 -- It's necessary because when we are dealing with a recursive
685 -- group, a variable late in the group might be mentioned
686 -- in the IdInfo of one early in the group
688 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
689 | isGlobalId bndr -- Injected binding for record selector, etc
690 = (bndr, tidyExpr rhs_tidy_env rhs)
694 bndr' = mkVanillaGlobal name' ty' idinfo'
695 ty' = tidyTopType (idType bndr)
696 rhs' = tidyExpr rhs_tidy_env rhs
697 idinfo' = tidyTopIdInfo rhs_tidy_env (isJust maybe_external)
698 (idInfo bndr) unfold_info arity
701 -- Expose an unfolding if ext_ids tells us to
702 -- Remember that ext_ids maps an Id to a Bool:
703 -- True to show the unfolding, False to hide it
704 maybe_external = lookupVarEnv ext_ids bndr
705 show_unfold = maybe_external `orElse` False
706 unfold_info | show_unfold = mkTopUnfolding rhs'
707 | otherwise = noUnfolding
709 -- Usually the Id will have an accurate arity on it, because
710 -- the simplifier has just run, but not always.
711 -- One case I found was when the last thing the simplifier
712 -- did was to let-bind a non-atomic argument and then float
713 -- it to the top level. So it seems more robust just to
715 arity = exprArity rhs
718 -- tidyTopIdInfo creates the final IdInfo for top-level
719 -- binders. There are two delicate pieces:
721 -- * Arity. After CoreTidy, this arity must not change any more.
722 -- Indeed, CorePrep must eta expand where necessary to make
723 -- the manifest arity equal to the claimed arity.
725 -- * CAF info. This must also remain valid through to code generation.
726 -- We add the info here so that it propagates to all
727 -- occurrences of the binders in RHSs, and hence to occurrences in
728 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
729 -- CoreToStg makes use of this when constructing SRTs.
731 tidyTopIdInfo tidy_env is_external idinfo unfold_info arity caf_info
732 | not is_external -- For internal Ids (not externally visible)
733 = vanillaIdInfo -- we only need enough info for code generation
734 -- Arity and strictness info are enough;
735 -- c.f. CoreTidy.tidyLetBndr
736 `setCafInfo` caf_info
738 `setAllStrictnessInfo` newStrictnessInfo idinfo
740 | otherwise -- Externally-visible Ids get the whole lot
742 `setCafInfo` caf_info
744 `setAllStrictnessInfo` newStrictnessInfo idinfo
745 `setInlinePragInfo` inlinePragInfo idinfo
746 `setUnfoldingInfo` unfold_info
747 `setWorkerInfo` tidyWorker tidy_env (workerInfo idinfo)
748 -- NB: we throw away the Rules
749 -- They have already been extracted by findExternalRules
753 ------------ Worker --------------
754 tidyWorker tidy_env (HasWorker work_id wrap_arity)
755 = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
756 tidyWorker tidy_env other
760 %************************************************************************
762 \subsection{Figuring out CafInfo for an expression}
764 %************************************************************************
766 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
767 We mark such things as `MayHaveCafRefs' because this information is
768 used to decide whether a particular closure needs to be referenced
771 There are two reasons for setting MayHaveCafRefs:
772 a) The RHS is a CAF: a top-level updatable thunk.
773 b) The RHS refers to something that MayHaveCafRefs
775 Possible improvement: In an effort to keep the number of CAFs (and
776 hence the size of the SRTs) down, we could also look at the expression and
777 decide whether it requires a small bounded amount of heap, so we can ignore
778 it as a CAF. In these cases however, we would need to use an additional
779 CAF list to keep track of non-collectable CAFs.
782 hasCafRefs :: HomeModules -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
783 hasCafRefs hmods p arity expr
784 | is_caf || mentions_cafs = MayHaveCafRefs
785 | otherwise = NoCafRefs
787 mentions_cafs = isFastTrue (cafRefs p expr)
788 is_caf = not (arity > 0 || rhsIsStatic hmods expr)
789 -- NB. we pass in the arity of the expression, which is expected
790 -- to be calculated by exprArity. This is because exprArity
791 -- knows how much eta expansion is going to be done by
792 -- CorePrep later on, and we don't want to duplicate that
793 -- knowledge in rhsIsStatic below.
796 -- imported Ids first:
797 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
798 -- now Ids local to this module:
800 case lookupVarEnv p id of
801 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
802 Nothing -> fastBool False
804 cafRefs p (Lit l) = fastBool False
805 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
806 cafRefs p (Lam x e) = cafRefs p e
807 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
808 cafRefs p (Case e bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
809 cafRefs p (Note n e) = cafRefs p e
810 cafRefs p (Type t) = fastBool False
812 cafRefss p [] = fastBool False
813 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
815 -- hack for lazy-or over FastBool.
816 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))