2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section{Tidying up Core}
7 module TidyPgm( mkBootModDetailsDs, mkBootModDetailsTc, tidyProgram ) where
9 #include "HsVersions.h"
44 import FastBool hiding ( fastOr )
46 import Data.List ( partition )
47 import Data.Maybe ( isJust )
48 import Data.IORef ( IORef, readIORef, writeIORef )
50 _dummy :: FS.FastString
55 Constructing the TypeEnv, Instances, Rules from which the ModIface is
56 constructed, and which goes on to subsequent modules in --make mode.
58 Most of the interface file is obtained simply by serialising the
59 TypeEnv. One important consequence is that if the *interface file*
60 has pragma info if and only if the final TypeEnv does. This is not so
61 important for *this* module, but it's essential for ghc --make:
62 subsequent compilations must not see (e.g.) the arity if the interface
63 file does not contain arity If they do, they'll exploit the arity;
64 then the arity might change, but the iface file doesn't change =>
65 recompilation does not happen => disaster.
67 For data types, the final TypeEnv will have a TyThing for the TyCon,
68 plus one for each DataCon; the interface file will contain just one
69 data type declaration, but it is de-serialised back into a collection
72 %************************************************************************
76 %************************************************************************
79 Plan A: mkBootModDetails: omit pragmas, make interfaces small
80 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
83 * Drop all WiredIn things from the TypeEnv
84 (we never want them in interface files)
86 * Retain all TyCons and Classes in the TypeEnv, to avoid
87 having to find which ones are mentioned in the
90 * Trim off the constructors of non-exported TyCons, both
91 from the TyCon and from the TypeEnv
93 * Drop non-exported Ids from the TypeEnv
95 * Tidy the types of the DFunIds of Instances,
96 make them into GlobalIds, (they already have External Names)
97 and add them to the TypeEnv
99 * Tidy the types of the (exported) Ids in the TypeEnv,
100 make them into GlobalIds (they already have External Names)
102 * Drop rules altogether
104 * Tidy the bindings, to ensure that the Caf and Arity
105 information is correct for each top-level binder; the
106 code generator needs it. And to ensure that local names have
107 distinct OccNames in case of object-file splitting
110 -- This is Plan A: make a small type env when typechecking only,
111 -- or when compiling a hs-boot file, or simply when not using -O
113 -- We don't look at the bindings at all -- there aren't any
116 mkBootModDetailsTc :: HscEnv -> TcGblEnv -> IO ModDetails
117 mkBootModDetailsTc hsc_env
118 TcGblEnv{ tcg_exports = exports,
119 tcg_type_env = type_env,
121 tcg_fam_insts = fam_insts
123 = mkBootModDetails hsc_env exports type_env insts fam_insts
125 mkBootModDetailsDs :: HscEnv -> ModGuts -> IO ModDetails
126 mkBootModDetailsDs hsc_env
127 ModGuts{ mg_exports = exports,
130 mg_fam_insts = fam_insts
132 = mkBootModDetails hsc_env exports type_env insts fam_insts
134 mkBootModDetails :: HscEnv -> [AvailInfo] -> NameEnv TyThing
135 -> [Instance] -> [FamInstEnv.FamInst] -> IO ModDetails
136 mkBootModDetails hsc_env exports type_env insts fam_insts
137 = do { let dflags = hsc_dflags hsc_env
138 ; showPass dflags "Tidy [hoot] type env"
140 ; let { insts' = tidyInstances tidyExternalId insts
141 ; dfun_ids = map instanceDFunId insts'
142 ; type_env1 = tidyBootTypeEnv (availsToNameSet exports) type_env
143 ; type_env' = extendTypeEnvWithIds type_env1 dfun_ids
145 ; return (ModDetails { md_types = type_env'
147 , md_fam_insts = fam_insts
149 , md_exports = exports
150 , md_vect_info = noVectInfo
155 tidyBootTypeEnv :: NameSet -> TypeEnv -> TypeEnv
156 tidyBootTypeEnv exports type_env
157 = tidyTypeEnv True exports type_env final_ids
159 -- Find the LocalIds in the type env that are exported
160 -- Make them into GlobalIds, and tidy their types
162 -- It's very important to remove the non-exported ones
163 -- because we don't tidy the OccNames, and if we don't remove
164 -- the non-exported ones we'll get many things with the
165 -- same name in the interface file, giving chaos.
166 final_ids = [ tidyExternalId id
167 | id <- typeEnvIds type_env
171 -- default methods have their export flag set, but everything
172 -- else doesn't (yet), because this is pre-desugaring, so we
174 keep_it id = isExportedId id || idName id `elemNameSet` exports
177 tidyExternalId :: Id -> Id
178 -- Takes an LocalId with an External Name,
179 -- makes it into a GlobalId with VanillaIdInfo, and tidies its type
180 -- (NB: vanillaIdInfo makes a conservative assumption about Caf-hood.)
182 = ASSERT2( isLocalId id && isExternalName (idName id), ppr id )
183 mkVanillaGlobal (idName id) (tidyTopType (idType id)) vanillaIdInfo
187 %************************************************************************
189 Plan B: tidy bindings, make TypeEnv full of IdInfo
191 %************************************************************************
193 Plan B: include pragmas, make interfaces
194 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
195 * Figure out which Ids are externally visible
197 * Tidy the bindings, externalising appropriate Ids
199 * Drop all Ids from the TypeEnv, and add all the External Ids from
200 the bindings. (This adds their IdInfo to the TypeEnv; and adds
201 floated-out Ids that weren't even in the TypeEnv before.)
203 Step 1: Figure out external Ids
204 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
205 First we figure out which Ids are "external" Ids. An
206 "external" Id is one that is visible from outside the compilation
208 a) the user exported ones
209 b) ones mentioned in the unfoldings, workers,
210 or rules of externally-visible ones
211 This exercise takes a sweep of the bindings bottom to top. Actually,
212 in Step 2 we're also going to need to know which Ids should be
213 exported with their unfoldings, so we produce not an IdSet but an
217 Step 2: Tidy the program
218 ~~~~~~~~~~~~~~~~~~~~~~~~
219 Next we traverse the bindings top to bottom. For each *top-level*
222 1. Make it into a GlobalId; its IdDetails becomes VanillaGlobal,
223 reflecting the fact that from now on we regard it as a global,
226 2. Give it a system-wide Unique.
227 [Even non-exported things need system-wide Uniques because the
228 byte-code generator builds a single Name->BCO symbol table.]
230 We use the NameCache kept in the HscEnv as the
231 source of such system-wide uniques.
233 For external Ids, use the original-name cache in the NameCache
234 to ensure that the unique assigned is the same as the Id had
235 in any previous compilation run.
237 3. If it's an external Id, make it have a External Name, otherwise
238 make it have an Internal Name.
239 This is used by the code generator to decide whether
240 to make the label externally visible
242 4. Give external Ids a "tidy" OccName. This means
243 we can print them in interface files without confusing
244 "x" (unique 5) with "x" (unique 10).
246 5. Give it its UTTERLY FINAL IdInfo; in ptic,
247 * its unfolding, if it should have one
249 * its arity, computed from the number of visible lambdas
251 * its CAF info, computed from what is free in its RHS
254 Finally, substitute these new top-level binders consistently
255 throughout, including in unfoldings. We also tidy binders in
256 RHSs, so that they print nicely in interfaces.
259 tidyProgram :: HscEnv -> ModGuts -> IO (CgGuts, ModDetails)
261 (ModGuts { mg_module = mod, mg_exports = exports,
263 mg_insts = insts, mg_fam_insts = fam_insts,
265 mg_rules = imp_rules,
266 mg_vect_info = vect_info,
267 mg_dir_imps = dir_imps,
269 mg_foreign = foreign_stubs,
270 mg_hpc_info = hpc_info,
271 mg_modBreaks = modBreaks })
273 = do { let dflags = hsc_dflags hsc_env
274 ; showPass dflags "Tidy Core"
276 ; let { omit_prags = dopt Opt_OmitInterfacePragmas dflags
277 ; ext_ids = findExternalIds omit_prags binds
280 | otherwise = findExternalRules binds imp_rules ext_ids
281 -- findExternalRules filters imp_rules to avoid binders that
282 -- aren't externally visible; but the externally-visible binders
283 -- are computed (by findExternalIds) assuming that all orphan
284 -- rules are exported (they get their Exported flag set in the desugarer)
285 -- So in fact we may export more than we need.
286 -- (It's a sort of mutual recursion.)
289 ; (tidy_env, tidy_binds) <- tidyTopBinds hsc_env mod type_env ext_ids
292 ; let { export_set = availsToNameSet exports
293 ; final_ids = [ id | id <- bindersOfBinds tidy_binds,
294 isExternalName (idName id)]
295 ; tidy_type_env = tidyTypeEnv omit_prags export_set type_env
297 ; tidy_insts = tidyInstances (lookup_dfun tidy_type_env) insts
298 -- A DFunId will have a binding in tidy_binds, and so
299 -- will now be in final_env, replete with IdInfo
300 -- Its name will be unchanged since it was born, but
301 -- we want Global, IdInfo-rich (or not) DFunId in the
304 ; tidy_rules = tidyRules tidy_env ext_rules
305 -- You might worry that the tidy_env contains IdInfo-rich stuff
306 -- and indeed it does, but if omit_prags is on, ext_rules is
309 ; implicit_binds = getImplicitBinds type_env
310 ; all_tidy_binds = implicit_binds ++ tidy_binds
311 ; alg_tycons = filter isAlgTyCon (typeEnvTyCons type_env)
314 ; endPass dflags "Tidy Core" Opt_D_dump_simpl all_tidy_binds
315 ; dumpIfSet_core dflags Opt_D_dump_simpl
317 (pprRules tidy_rules)
319 ; let dir_imp_mods = map fst (moduleEnvElts dir_imps)
321 ; return (CgGuts { cg_module = mod,
322 cg_tycons = alg_tycons,
323 cg_binds = all_tidy_binds,
324 cg_dir_imps = dir_imp_mods,
325 cg_foreign = foreign_stubs,
326 cg_dep_pkgs = dep_pkgs deps,
327 cg_hpc_info = hpc_info,
328 cg_modBreaks = modBreaks },
330 ModDetails { md_types = tidy_type_env,
331 md_rules = tidy_rules,
332 md_insts = tidy_insts,
333 md_fam_insts = fam_insts,
334 md_exports = exports,
335 md_vect_info = vect_info -- is already tidy
339 lookup_dfun :: TypeEnv -> Var -> Id
340 lookup_dfun type_env dfun_id
341 = case lookupTypeEnv type_env (idName dfun_id) of
342 Just (AnId dfun_id') -> dfun_id'
343 _other -> pprPanic "lookup_dfun" (ppr dfun_id)
345 --------------------------
346 tidyTypeEnv :: Bool -> NameSet -> TypeEnv -> [Id] -> TypeEnv
348 -- The competed type environment is gotten from
349 -- Dropping any wired-in things, and then
350 -- a) keeping the types and classes
351 -- b) removing all Ids,
352 -- c) adding Ids with correct IdInfo, including unfoldings,
353 -- gotten from the bindings
354 -- From (c) we keep only those Ids with External names;
355 -- the CoreTidy pass makes sure these are all and only
356 -- the externally-accessible ones
357 -- This truncates the type environment to include only the
358 -- exported Ids and things needed from them, which saves space
360 tidyTypeEnv omit_prags exports type_env final_ids
361 = let type_env1 = filterNameEnv keep_it type_env
362 type_env2 = extendTypeEnvWithIds type_env1 final_ids
363 type_env3 | omit_prags = mapNameEnv (trimThing exports) type_env2
364 | otherwise = type_env2
368 -- We keep GlobalIds, because they won't appear
369 -- in the bindings from which final_ids are derived!
370 -- (The bindings bind LocalIds.)
371 keep_it thing | isWiredInThing thing = False
372 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
373 keep_it _other = True -- Keep all TyCons, DataCons, and Classes
375 --------------------------
376 isWiredInThing :: TyThing -> Bool
377 isWiredInThing thing = isWiredInName (getName thing)
379 --------------------------
380 trimThing :: NameSet -> TyThing -> TyThing
381 -- Trim off inessentials, for boot files and no -O
382 trimThing exports (ATyCon tc)
383 | not (mustExposeTyCon exports tc)
384 = ATyCon (makeTyConAbstract tc)
386 trimThing _exports (AnId id)
387 | not (isImplicitId id)
388 = AnId (id `setIdInfo` vanillaIdInfo)
390 trimThing _exports other_thing
394 mustExposeTyCon :: NameSet -- Exports
395 -> TyCon -- The tycon
396 -> Bool -- Can its rep be hidden?
397 -- We are compiling without -O, and thus trying to write as little as
398 -- possible into the interface file. But we must expose the details of
399 -- any data types whose constructors or fields are exported
400 mustExposeTyCon exports tc
401 | not (isAlgTyCon tc) -- Synonyms
403 | isEnumerationTyCon tc -- For an enumeration, exposing the constructors
404 = True -- won't lead to the need for further exposure
405 -- (This includes data types with no constructors.)
406 | isOpenTyCon tc -- Open type family
409 | otherwise -- Newtype, datatype
410 = any exported_con (tyConDataCons tc)
411 -- Expose rep if any datacon or field is exported
413 || (isNewTyCon tc && isFFITy (snd (newTyConRhs tc)))
414 -- Expose the rep for newtypes if the rep is an FFI type.
415 -- For a very annoying reason. 'Foreign import' is meant to
416 -- be able to look through newtypes transparently, but it
417 -- can only do that if it can "see" the newtype representation
419 exported_con con = any (`elemNameSet` exports)
420 (dataConName con : dataConFieldLabels con)
422 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
423 tidyInstances tidy_dfun ispecs
426 tidy ispec = setInstanceDFunId ispec $
427 tidy_dfun (instanceDFunId ispec)
429 getImplicitBinds :: TypeEnv -> [CoreBind]
430 getImplicitBinds type_env
431 = map get_defn (concatMap implicit_con_ids (typeEnvTyCons type_env)
432 ++ concatMap other_implicit_ids (typeEnvElts type_env))
433 -- Put the constructor wrappers first, because
434 -- other implicit bindings (notably the fromT functions arising
435 -- from generics) use the constructor wrappers. At least that's
436 -- what External Core likes
438 implicit_con_ids tc = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
440 other_implicit_ids (ATyCon tc) = filter (not . isNaughtyRecordSelector) (tyConSelIds tc)
441 -- The "naughty" ones are not real functions at all
442 -- They are there just so we can get decent error messages
443 -- See Note [Naughty record selectors] in MkId.lhs
444 other_implicit_ids (AClass cl) = classSelIds cl
445 other_implicit_ids _other = []
447 get_defn :: Id -> CoreBind
448 get_defn id = NonRec id (tidyExpr emptyTidyEnv rhs)
450 rhs = unfoldingTemplate (idUnfolding id)
451 -- Don't forget to tidy the body ! Otherwise you get silly things like
452 -- \ tpl -> case tpl of tpl -> (tpl,tpl) -> tpl
456 %************************************************************************
458 \subsection{Step 1: finding externals}
460 %************************************************************************
463 findExternalIds :: Bool
465 -> IdEnv Bool -- In domain => external
466 -- Range = True <=> show unfolding
467 -- Step 1 from the notes above
468 findExternalIds omit_prags binds
470 = mkVarEnv [ (id,False) | id <- bindersOfBinds binds, isExportedId id ]
473 = foldr find emptyVarEnv binds
475 find (NonRec id rhs) needed
476 | need_id needed id = addExternal (id,rhs) needed
478 find (Rec prs) needed = find_prs prs needed
480 -- For a recursive group we have to look for a fixed point
482 | null needed_prs = needed
483 | otherwise = find_prs other_prs new_needed
485 (needed_prs, other_prs) = partition (need_pr needed) prs
486 new_needed = foldr addExternal needed needed_prs
488 -- The 'needed' set contains the Ids that are needed by earlier
489 -- interface file emissions. If the Id isn't in this set, and isn't
490 -- exported, there's no need to emit anything
491 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
492 need_pr needed_set (id,_) = need_id needed_set id
494 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
495 -- The Id is needed; extend the needed set
496 -- with it and its dependents (free vars etc)
497 addExternal (id,rhs) needed
498 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
501 add_occ id needed | id `elemVarEnv` needed = needed
502 | otherwise = extendVarEnv needed id False
503 -- "False" because we don't know we need the Id's unfolding
504 -- Don't override existing bindings; we might have already set it to True
506 new_needed_ids = worker_ids `unionVarSet`
507 unfold_ids `unionVarSet`
511 dont_inline = isNeverActive (inlinePragInfo idinfo)
512 loop_breaker = isNonRuleLoopBreaker (occInfo idinfo)
513 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
514 spec_ids = specInfoFreeVars (specInfo idinfo)
515 worker_info = workerInfo idinfo
517 -- Stuff to do with the Id's unfolding
518 -- The simplifier has put an up-to-date unfolding
519 -- in the IdInfo, but the RHS will do just as well
520 unfolding = unfoldingInfo idinfo
521 rhs_is_small = not (neverUnfold unfolding)
523 -- We leave the unfolding there even if there is a worker
524 -- In GHCI the unfolding is used by importers
525 -- When writing an interface file, we omit the unfolding
526 -- if there is a worker
527 show_unfold = not bottoming_fn && -- Not necessary
530 rhs_is_small -- Small enough
532 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
533 | otherwise = emptyVarSet
535 worker_ids = case worker_info of
536 HasWorker work_id _ -> unitVarSet work_id
537 _otherwise -> emptyVarSet
542 findExternalRules :: [CoreBind]
543 -> [CoreRule] -- Non-local rules (i.e. ones for imported fns)
544 -> IdEnv a -- Ids that are exported, so we need their rules
546 -- The complete rules are gotten by combining
547 -- a) the non-local rules
548 -- b) rules embedded in the top-level Ids
549 findExternalRules binds non_local_rules ext_ids
550 = filter (not . internal_rule) (non_local_rules ++ local_rules)
553 | id <- bindersOfBinds binds,
554 id `elemVarEnv` ext_ids,
555 rule <- idCoreRules id
559 = any internal_id (varSetElems (ruleLhsFreeIds rule))
560 -- Don't export a rule whose LHS mentions a locally-defined
561 -- Id that is completely internal (i.e. not visible to an
564 internal_id id = not (id `elemVarEnv` ext_ids)
569 %************************************************************************
571 \subsection{Step 2: top-level tidying}
573 %************************************************************************
577 -- TopTidyEnv: when tidying we need to know
578 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
579 -- These may have arisen because the
580 -- renamer read in an interface file mentioning M.$wf, say,
581 -- and assigned it unique r77. If, on this compilation, we've
582 -- invented an Id whose name is $wf (but with a different unique)
583 -- we want to rename it to have unique r77, so that we can do easy
584 -- comparisons with stuff from the interface file
586 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
589 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
591 tidyTopBinds :: HscEnv
594 -> IdEnv Bool -- Domain = Ids that should be external
595 -- True <=> their unfolding is external too
597 -> IO (TidyEnv, [CoreBind])
599 tidyTopBinds hsc_env mod type_env ext_ids binds
600 = tidy init_env binds
602 nc_var = hsc_NC hsc_env
604 -- We also make sure to avoid any exported binders. Consider
605 -- f{-u1-} = 1 -- Local decl
607 -- f{-u2-} = 2 -- Exported decl
609 -- The second exported decl must 'get' the name 'f', so we
610 -- have to put 'f' in the avoids list before we get to the first
611 -- decl. tidyTopId then does a no-op on exported binders.
612 init_env = (initTidyOccEnv avoids, emptyVarEnv)
613 avoids = [getOccName name | bndr <- typeEnvIds type_env,
614 let name = idName bndr,
616 -- In computing our "avoids" list, we must include
618 -- all things with global names (assigned once and for
619 -- all by the renamer)
620 -- since their names are "taken".
621 -- The type environment is a convenient source of such things.
623 this_pkg = thisPackage (hsc_dflags hsc_env)
625 tidy env [] = return (env, [])
626 tidy env (b:bs) = do { (env1, b') <- tidyTopBind this_pkg mod nc_var ext_ids env b
627 ; (env2, bs') <- tidy env1 bs
628 ; return (env2, b':bs') }
630 ------------------------
631 tidyTopBind :: PackageId
633 -> IORef NameCache -- For allocating new unique names
634 -> IdEnv Bool -- Domain = Ids that should be external
635 -- True <=> their unfolding is external too
636 -> TidyEnv -> CoreBind
637 -> IO (TidyEnv, CoreBind)
639 tidyTopBind this_pkg mod nc_var ext_ids (occ_env1,subst1) (NonRec bndr rhs)
640 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
641 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
642 ; subst2 = extendVarEnv subst1 bndr bndr'
643 ; tidy_env2 = (occ_env2, subst2) }
644 ; return (tidy_env2, NonRec bndr' rhs') }
646 caf_info = hasCafRefs this_pkg subst1 (idArity bndr) rhs
648 tidyTopBind this_pkg mod nc_var ext_ids (occ_env1,subst1) (Rec prs)
649 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
650 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
652 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
653 ; tidy_env2 = (occ_env2, subst2) }
654 ; return (tidy_env2, Rec prs') }
658 -- the CafInfo for a recursive group says whether *any* rhs in
659 -- the group may refer indirectly to a CAF (because then, they all do).
661 | or [ mayHaveCafRefs (hasCafRefs this_pkg subst1 (idArity bndr) rhs)
662 | (bndr,rhs) <- prs ] = MayHaveCafRefs
663 | otherwise = NoCafRefs
665 --------------------------------------------------------------------
667 -- This is where we set names to local/global based on whether they really are
668 -- externally visible (see comment at the top of this module). If the name
669 -- was previously local, we have to give it a unique occurrence name if
670 -- we intend to externalise it.
671 tidyTopNames :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
672 -> [Id] -> IO (TidyOccEnv, [Name])
673 tidyTopNames _mod _nc_var _ext_ids occ_env [] = return (occ_env, [])
674 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
675 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
676 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
677 ; return (occ_env2, name:names) }
679 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
680 -> Id -> IO (TidyOccEnv, Name)
681 tidyTopName mod nc_var ext_ids occ_env id
682 | global && internal = return (occ_env, localiseName name)
684 | global && external = return (occ_env, name)
685 -- Global names are assumed to have been allocated by the renamer,
686 -- so they already have the "right" unique
687 -- And it's a system-wide unique too
689 -- Now we get to the real reason that all this is in the IO Monad:
690 -- we have to update the name cache in a nice atomic fashion
692 | local && internal = do { nc <- readIORef nc_var
693 ; let (nc', new_local_name) = mk_new_local nc
694 ; writeIORef nc_var nc'
695 ; return (occ_env', new_local_name) }
696 -- Even local, internal names must get a unique occurrence, because
697 -- if we do -split-objs we externalise the name later, in the code generator
699 -- Similarly, we must make sure it has a system-wide Unique, because
700 -- the byte-code generator builds a system-wide Name->BCO symbol table
702 | local && external = do { nc <- readIORef nc_var
703 ; let (nc', new_external_name) = mk_new_external nc
704 ; writeIORef nc_var nc'
705 ; return (occ_env', new_external_name) }
707 | otherwise = panic "tidyTopName"
710 external = id `elemVarEnv` ext_ids
711 global = isExternalName name
713 internal = not external
714 loc = nameSrcSpan name
716 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
718 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
720 (us1, us2) = splitUniqSupply (nsUniqs nc)
721 uniq = uniqFromSupply us1
723 mk_new_external nc = allocateGlobalBinder nc mod occ' loc
724 -- If we want to externalise a currently-local name, check
725 -- whether we have already assigned a unique for it.
726 -- If so, use it; if not, extend the table.
727 -- All this is done by allcoateGlobalBinder.
728 -- This is needed when *re*-compiling a module in GHCi; we must
729 -- use the same name for externally-visible things as we did before.
732 -----------------------------------------------------------
733 tidyTopPair :: VarEnv Bool
734 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
735 -- It is knot-tied: don't look at it!
738 -> (Id, CoreExpr) -- Binder and RHS before tidying
740 -- This function is the heart of Step 2
741 -- The rec_tidy_env is the one to use for the IdInfo
742 -- It's necessary because when we are dealing with a recursive
743 -- group, a variable late in the group might be mentioned
744 -- in the IdInfo of one early in the group
746 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
747 | isGlobalId bndr -- Injected binding for record selector, etc
748 = (bndr, tidyExpr rhs_tidy_env rhs)
752 bndr' = mkVanillaGlobal name' ty' idinfo'
753 ty' = tidyTopType (idType bndr)
754 rhs' = tidyExpr rhs_tidy_env rhs
756 idinfo' = tidyTopIdInfo (isJust maybe_external)
757 idinfo unfold_info worker_info
760 -- Expose an unfolding if ext_ids tells us to
761 -- Remember that ext_ids maps an Id to a Bool:
762 -- True to show the unfolding, False to hide it
763 maybe_external = lookupVarEnv ext_ids bndr
764 show_unfold = maybe_external `orElse` False
765 unfold_info | show_unfold = mkTopUnfolding rhs'
766 | otherwise = noUnfolding
767 worker_info = tidyWorker rhs_tidy_env show_unfold (workerInfo idinfo)
769 -- Usually the Id will have an accurate arity on it, because
770 -- the simplifier has just run, but not always.
771 -- One case I found was when the last thing the simplifier
772 -- did was to let-bind a non-atomic argument and then float
773 -- it to the top level. So it seems more robust just to
775 arity = exprArity rhs
778 -- tidyTopIdInfo creates the final IdInfo for top-level
779 -- binders. There are two delicate pieces:
781 -- * Arity. After CoreTidy, this arity must not change any more.
782 -- Indeed, CorePrep must eta expand where necessary to make
783 -- the manifest arity equal to the claimed arity.
785 -- * CAF info. This must also remain valid through to code generation.
786 -- We add the info here so that it propagates to all
787 -- occurrences of the binders in RHSs, and hence to occurrences in
788 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
789 -- CoreToStg makes use of this when constructing SRTs.
790 tidyTopIdInfo :: Bool -> IdInfo -> Unfolding
791 -> WorkerInfo -> ArityInfo -> CafInfo
793 tidyTopIdInfo is_external idinfo unfold_info worker_info arity caf_info
794 | not is_external -- For internal Ids (not externally visible)
795 = vanillaIdInfo -- we only need enough info for code generation
796 -- Arity and strictness info are enough;
797 -- c.f. CoreTidy.tidyLetBndr
798 `setCafInfo` caf_info
800 `setAllStrictnessInfo` newStrictnessInfo idinfo
802 | otherwise -- Externally-visible Ids get the whole lot
804 `setCafInfo` caf_info
806 `setAllStrictnessInfo` newStrictnessInfo idinfo
807 `setInlinePragInfo` inlinePragInfo idinfo
808 `setUnfoldingInfo` unfold_info
809 `setWorkerInfo` worker_info
810 -- NB: we throw away the Rules
811 -- They have already been extracted by findExternalRules
815 ------------ Worker --------------
816 tidyWorker :: TidyEnv -> Bool -> WorkerInfo -> WorkerInfo
817 tidyWorker _tidy_env _show_unfold NoWorker
819 tidyWorker tidy_env show_unfold (HasWorker work_id wrap_arity)
820 | show_unfold = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
821 | otherwise = NoWorker
822 -- NB: do *not* expose the worker if show_unfold is off,
823 -- because that means this thing is a loop breaker or
824 -- marked NOINLINE or something like that
825 -- This is important: if you expose the worker for a loop-breaker
826 -- then you can make the simplifier go into an infinite loop, because
827 -- in effect the unfolding is exposed. See Trac #1709
829 -- You might think that if show_unfold is False, then the thing should
830 -- not be w/w'd in the first place. But a legitimate reason is this:
831 -- the function returns bottom
832 -- In this case, show_unfold will be false (we don't expose unfoldings
833 -- for bottoming functions), but we might still have a worker/wrapper
834 -- split (see Note [Worker-wrapper for bottoming functions] in WorkWrap.lhs
837 %************************************************************************
839 \subsection{Figuring out CafInfo for an expression}
841 %************************************************************************
843 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
844 We mark such things as `MayHaveCafRefs' because this information is
845 used to decide whether a particular closure needs to be referenced
848 There are two reasons for setting MayHaveCafRefs:
849 a) The RHS is a CAF: a top-level updatable thunk.
850 b) The RHS refers to something that MayHaveCafRefs
852 Possible improvement: In an effort to keep the number of CAFs (and
853 hence the size of the SRTs) down, we could also look at the expression and
854 decide whether it requires a small bounded amount of heap, so we can ignore
855 it as a CAF. In these cases however, we would need to use an additional
856 CAF list to keep track of non-collectable CAFs.
859 hasCafRefs :: PackageId -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
860 hasCafRefs this_pkg p arity expr
861 | is_caf || mentions_cafs
863 | otherwise = NoCafRefs
865 mentions_cafs = isFastTrue (cafRefs p expr)
866 is_caf = not (arity > 0 || rhsIsStatic this_pkg expr)
868 -- NB. we pass in the arity of the expression, which is expected
869 -- to be calculated by exprArity. This is because exprArity
870 -- knows how much eta expansion is going to be done by
871 -- CorePrep later on, and we don't want to duplicate that
872 -- knowledge in rhsIsStatic below.
874 cafRefs :: VarEnv Id -> Expr a -> FastBool
876 -- imported Ids first:
877 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
878 -- now Ids local to this module:
880 case lookupVarEnv p id of
881 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
882 Nothing -> fastBool False
884 cafRefs _ (Lit _) = fastBool False
885 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
886 cafRefs p (Lam _ e) = cafRefs p e
887 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
888 cafRefs p (Case e _bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
889 cafRefs p (Note _n e) = cafRefs p e
890 cafRefs p (Cast e _co) = cafRefs p e
891 cafRefs _ (Type _) = fastBool False
893 cafRefss :: VarEnv Id -> [Expr a] -> FastBool
894 cafRefss _ [] = fastBool False
895 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
897 fastOr :: FastBool -> (a -> FastBool) -> a -> FastBool
898 -- hack for lazy-or over FastBool.
899 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))