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(..), DynFlags(..), dopt )
13 import CoreUnfold ( noUnfolding, mkTopUnfolding )
14 import CoreFVs ( ruleLhsFreeIds, exprSomeFreeVars )
15 import CoreTidy ( tidyExpr, tidyVarOcc, tidyRules )
16 import PprCore ( pprRules )
17 import CoreLint ( showPass, endPass )
18 import CoreUtils ( exprArity, rhsIsStatic )
21 import Var ( Id, Var )
22 import Id ( idType, idInfo, idName, idCoreRules, isGlobalId,
23 isExportedId, mkVanillaGlobal, isLocalId, isNaughtyRecordSelector,
24 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, isNonRuleLoopBreaker )
31 import Name ( Name, getOccName, nameOccName, mkInternalName,
32 localiseName, isExternalName, nameSrcLoc,
33 isWiredInName, getName
35 import NameSet ( NameSet, elemNameSet, filterNameSet )
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,
44 isEnumerationTyCon, isOpenTyCon )
45 import Class ( classSelIds )
46 import Module ( Module )
48 import Maybes ( orElse, mapCatMaybes )
49 import ErrUtils ( showPass, dumpIfSet_core )
50 import PackageConfig ( PackageId )
51 import UniqSupply ( splitUniqSupply, uniqFromSupply )
53 import FastTypes hiding ( fastOr )
55 import Data.List ( partition )
56 import Data.Maybe ( isJust )
57 import Data.IORef ( IORef, readIORef, writeIORef )
61 Constructing the TypeEnv, Instances, Rules from which the ModIface is
62 constructed, and which goes on to subsequent modules in --make mode.
64 Most of the interface file is obtained simply by serialising the
65 TypeEnv. One important consequence is that if the *interface file*
66 has pragma info if and only if the final TypeEnv does. This is not so
67 important for *this* module, but it's essential for ghc --make:
68 subsequent compilations must not see (e.g.) the arity if the interface
69 file does not contain arity If they do, they'll exploit the arity;
70 then the arity might change, but the iface file doesn't change =>
71 recompilation does not happen => disaster.
73 For data types, the final TypeEnv will have a TyThing for the TyCon,
74 plus one for each DataCon; the interface file will contain just one
75 data type declaration, but it is de-serialised back into a collection
78 %************************************************************************
82 %************************************************************************
85 Plan A: mkBootModDetails: omit pragmas, make interfaces small
86 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
89 * Drop all WiredIn things from the TypeEnv
90 (we never want them in interface files)
92 * Retain all TyCons and Classes in the TypeEnv, to avoid
93 having to find which ones are mentioned in the
96 * Trim off the constructors of non-exported TyCons, both
97 from the TyCon and from the TypeEnv
99 * Drop non-exported Ids from the TypeEnv
101 * Tidy the types of the DFunIds of Instances,
102 make them into GlobalIds, (they already have External Names)
103 and add them to the TypeEnv
105 * Tidy the types of the (exported) Ids in the TypeEnv,
106 make them into GlobalIds (they already have External Names)
108 * Drop rules altogether
110 * Tidy the bindings, to ensure that the Caf and Arity
111 information is correct for each top-level binder; the
112 code generator needs it. And to ensure that local names have
113 distinct OccNames in case of object-file splitting
116 mkBootModDetails :: HscEnv -> ModGuts -> IO ModDetails
117 -- This is Plan A: make a small type env when typechecking only,
118 -- or when compiling a hs-boot file, or simply when not using -O
120 -- We don't look at the bindings at all -- there aren't any
123 mkBootModDetails hsc_env (ModGuts { mg_module = mod
124 , mg_exports = exports
125 , mg_types = type_env
127 , mg_fam_insts = fam_insts
128 , mg_modBreaks = modBreaks
130 = do { let dflags = hsc_dflags hsc_env
131 ; showPass dflags "Tidy [hoot] type env"
133 ; let { insts' = tidyInstances tidyExternalId insts
134 ; type_env1 = filterNameEnv (not . isWiredInThing) type_env
135 ; type_env2 = mapNameEnv tidyBootThing type_env1
136 ; type_env' = extendTypeEnvWithIds type_env2
137 (map instanceDFunId insts')
139 ; return (ModDetails { md_types = type_env'
141 , md_fam_insts = fam_insts
143 , md_exports = exports
144 , md_modBreaks = modBreaks
145 , md_vect_info = noVectInfo
150 isWiredInThing :: TyThing -> Bool
151 isWiredInThing thing = isWiredInName (getName thing)
153 tidyBootThing :: TyThing -> TyThing
154 -- Just externalise the Ids; keep everything
155 tidyBootThing (AnId id) | isLocalId id = AnId (tidyExternalId id)
156 tidyBootThing thing = thing
158 tidyExternalId :: Id -> Id
159 -- Takes an LocalId with an External Name,
160 -- makes it into a GlobalId with VanillaIdInfo, and tidies its type
161 -- (NB: vanillaIdInfo makes a conservative assumption about Caf-hood.)
163 = ASSERT2( isLocalId id && isExternalName (idName id), ppr id )
164 mkVanillaGlobal (idName id) (tidyTopType (idType id)) vanillaIdInfo
168 %************************************************************************
170 Plan B: tidy bindings, make TypeEnv full of IdInfo
172 %************************************************************************
174 Plan B: include pragmas, make interfaces
175 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
176 * Figure out which Ids are externally visible
178 * Tidy the bindings, externalising appropriate Ids
180 * Drop all Ids from the TypeEnv, and add all the External Ids from
181 the bindings. (This adds their IdInfo to the TypeEnv; and adds
182 floated-out Ids that weren't even in the TypeEnv before.)
184 Step 1: Figure out external Ids
185 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
186 First we figure out which Ids are "external" Ids. An
187 "external" Id is one that is visible from outside the compilation
189 a) the user exported ones
190 b) ones mentioned in the unfoldings, workers,
191 or rules of externally-visible ones
192 This exercise takes a sweep of the bindings bottom to top. Actually,
193 in Step 2 we're also going to need to know which Ids should be
194 exported with their unfoldings, so we produce not an IdSet but an
198 Step 2: Tidy the program
199 ~~~~~~~~~~~~~~~~~~~~~~~~
200 Next we traverse the bindings top to bottom. For each *top-level*
203 1. Make it into a GlobalId; its IdDetails becomes VanillaGlobal,
204 reflecting the fact that from now on we regard it as a global,
207 2. Give it a system-wide Unique.
208 [Even non-exported things need system-wide Uniques because the
209 byte-code generator builds a single Name->BCO symbol table.]
211 We use the NameCache kept in the HscEnv as the
212 source of such system-wide uniques.
214 For external Ids, use the original-name cache in the NameCache
215 to ensure that the unique assigned is the same as the Id had
216 in any previous compilation run.
218 3. If it's an external Id, make it have a External Name, otherwise
219 make it have an Internal Name.
220 This is used by the code generator to decide whether
221 to make the label externally visible
223 4. Give external Ids a "tidy" OccName. This means
224 we can print them in interface files without confusing
225 "x" (unique 5) with "x" (unique 10).
227 5. Give it its UTTERLY FINAL IdInfo; in ptic,
228 * its unfolding, if it should have one
230 * its arity, computed from the number of visible lambdas
232 * its CAF info, computed from what is free in its RHS
235 Finally, substitute these new top-level binders consistently
236 throughout, including in unfoldings. We also tidy binders in
237 RHSs, so that they print nicely in interfaces.
240 tidyProgram :: HscEnv -> ModGuts -> IO (CgGuts, ModDetails)
242 mod_impl@(ModGuts { mg_module = mod, mg_exports = exports,
244 mg_insts = insts, mg_fam_insts = fam_insts,
246 mg_rules = imp_rules,
247 mg_vect_info = vect_info,
248 mg_dir_imps = dir_imps, mg_deps = deps,
249 mg_foreign = foreign_stubs,
250 mg_hpc_info = hpc_info,
251 mg_modBreaks = modBreaks })
253 = do { let dflags = hsc_dflags hsc_env
254 ; showPass dflags "Tidy Core"
256 ; let { omit_prags = dopt Opt_OmitInterfacePragmas dflags
257 ; ext_ids = findExternalIds omit_prags binds
260 | otherwise = findExternalRules binds imp_rules ext_ids
261 -- findExternalRules filters imp_rules to avoid binders that
262 -- aren't externally visible; but the externally-visible binders
263 -- are computed (by findExternalIds) assuming that all orphan
264 -- rules are exported (they get their Exported flag set in the desugarer)
265 -- So in fact we may export more than we need.
266 -- (It's a sort of mutual recursion.)
269 ; (tidy_env, tidy_binds) <- tidyTopBinds hsc_env mod type_env ext_ids
272 ; let { export_set = availsToNameSet exports
273 ; tidy_type_env = tidyTypeEnv omit_prags export_set type_env
275 ; tidy_insts = tidyInstances (lookup_dfun tidy_type_env) insts
276 -- A DFunId will have a binding in tidy_binds, and so
277 -- will now be in final_env, replete with IdInfo
278 -- Its name will be unchanged since it was born, but
279 -- we want Global, IdInfo-rich (or not) DFunId in the
282 ; tidy_rules = tidyRules tidy_env ext_rules
283 -- You might worry that the tidy_env contains IdInfo-rich stuff
284 -- and indeed it does, but if omit_prags is on, ext_rules is
287 ; implicit_binds = getImplicitBinds type_env
288 ; all_tidy_binds = implicit_binds ++ tidy_binds
289 ; alg_tycons = filter isAlgTyCon (typeEnvTyCons type_env)
291 ; tidy_vect_info = VectInfo
292 (filterNameSet (isElemId type_env)
293 (vectInfoCCVar vect_info))
294 -- filter against `type_env', not `tidy_type_env', as we must
295 -- keep all implicit names
298 ; endPass dflags "Tidy Core" Opt_D_dump_simpl all_tidy_binds
299 ; dumpIfSet_core dflags Opt_D_dump_simpl
301 (pprRules tidy_rules)
303 ; return (CgGuts { cg_module = mod,
304 cg_tycons = alg_tycons,
305 cg_binds = all_tidy_binds,
306 cg_dir_imps = dir_imps,
307 cg_foreign = foreign_stubs,
308 cg_dep_pkgs = dep_pkgs deps,
309 cg_hpc_info = hpc_info },
311 ModDetails { md_types = tidy_type_env,
312 md_rules = tidy_rules,
313 md_insts = tidy_insts,
314 md_fam_insts = fam_insts,
315 md_exports = exports,
316 md_modBreaks = modBreaks,
317 md_vect_info = tidy_vect_info
321 lookup_dfun type_env dfun_id
322 = case lookupTypeEnv type_env (idName dfun_id) of
323 Just (AnId dfun_id') -> dfun_id'
324 other -> pprPanic "lookup_dfun" (ppr dfun_id)
326 isElemId type_env name
327 = case lookupTypeEnv type_env name of
328 Just (AnId _) -> True
331 tidyTypeEnv :: Bool -> NameSet -> TypeEnv -> [CoreBind] -> TypeEnv
333 -- The competed type environment is gotten from
334 -- Dropping any wired-in things, and then
335 -- a) keeping the types and classes
336 -- b) removing all Ids,
337 -- c) adding Ids with correct IdInfo, including unfoldings,
338 -- gotten from the bindings
339 -- From (c) we keep only those Ids with External names;
340 -- the CoreTidy pass makes sure these are all and only
341 -- the externally-accessible ones
342 -- This truncates the type environment to include only the
343 -- exported Ids and things needed from them, which saves space
345 tidyTypeEnv omit_prags exports type_env tidy_binds
346 = let type_env1 = filterNameEnv keep_it type_env
347 type_env2 = extendTypeEnvWithIds type_env1 final_ids
348 type_env3 | omit_prags = mapNameEnv trim_thing type_env2
349 | otherwise = type_env2
353 final_ids = [ id | id <- bindersOfBinds tidy_binds,
354 isExternalName (idName id)]
356 -- We keep GlobalIds, because they won't appear
357 -- in the bindings from which final_ids are derived!
358 -- (The bindings bind LocalIds.)
359 keep_it thing | isWiredInThing thing = False
360 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
361 keep_it other = True -- Keep all TyCons, DataCons, and Classes
365 ATyCon tc | mustExposeTyCon exports tc -> thing
366 | otherwise -> ATyCon (makeTyConAbstract tc)
368 AnId id | isImplicitId id -> thing
369 | otherwise -> AnId (id `setIdInfo` vanillaIdInfo)
373 mustExposeTyCon :: NameSet -- Exports
374 -> TyCon -- The tycon
375 -> Bool -- Can its rep be hidden?
376 -- We are compiling without -O, and thus trying to write as little as
377 -- possible into the interface file. But we must expose the details of
378 -- any data types whose constructors or fields are exported
379 mustExposeTyCon exports tc
380 | not (isAlgTyCon tc) -- Synonyms
382 | isEnumerationTyCon tc -- For an enumeration, exposing the constructors
383 = True -- won't lead to the need for further exposure
384 -- (This includes data types with no constructors.)
385 | isOpenTyCon tc -- open type family
387 | otherwise -- Newtype, datatype
388 = any exported_con (tyConDataCons tc)
389 -- Expose rep if any datacon or field is exported
391 || (isNewTyCon tc && isFFITy (snd (newTyConRep tc)))
392 -- Expose the rep for newtypes if the rep is an FFI type.
393 -- For a very annoying reason. 'Foreign import' is meant to
394 -- be able to look through newtypes transparently, but it
395 -- can only do that if it can "see" the newtype representation
397 exported_con con = any (`elemNameSet` exports)
398 (dataConName con : dataConFieldLabels con)
400 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
401 tidyInstances tidy_dfun ispecs
404 tidy ispec = setInstanceDFunId ispec $
405 tidy_dfun (instanceDFunId ispec)
407 getImplicitBinds :: TypeEnv -> [CoreBind]
408 getImplicitBinds type_env
409 = map get_defn (concatMap implicit_con_ids (typeEnvTyCons type_env)
410 ++ concatMap other_implicit_ids (typeEnvElts type_env))
411 -- Put the constructor wrappers first, because
412 -- other implicit bindings (notably the fromT functions arising
413 -- from generics) use the constructor wrappers. At least that's
414 -- what External Core likes
416 implicit_con_ids tc = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
418 other_implicit_ids (ATyCon tc) = filter (not . isNaughtyRecordSelector) (tyConSelIds tc)
419 -- The "naughty" ones are not real functions at all
420 -- They are there just so we can get decent error messages
421 -- See Note [Naughty record selectors] in MkId.lhs
422 other_implicit_ids (AClass cl) = classSelIds cl
423 other_implicit_ids other = []
425 get_defn :: Id -> CoreBind
426 get_defn id = NonRec id (tidyExpr emptyTidyEnv rhs)
428 rhs = unfoldingTemplate (idUnfolding id)
429 -- Don't forget to tidy the body ! Otherwise you get silly things like
430 -- \ tpl -> case tpl of tpl -> (tpl,tpl) -> tpl
434 %************************************************************************
436 \subsection{Step 1: finding externals}
438 %************************************************************************
441 findExternalIds :: Bool
443 -> IdEnv Bool -- In domain => external
444 -- Range = True <=> show unfolding
445 -- Step 1 from the notes above
446 findExternalIds omit_prags binds
448 = mkVarEnv [ (id,False) | id <- bindersOfBinds binds, isExportedId id ]
451 = foldr find emptyVarEnv binds
453 find (NonRec id rhs) needed
454 | need_id needed id = addExternal (id,rhs) needed
456 find (Rec prs) needed = find_prs prs needed
458 -- For a recursive group we have to look for a fixed point
460 | null needed_prs = needed
461 | otherwise = find_prs other_prs new_needed
463 (needed_prs, other_prs) = partition (need_pr needed) prs
464 new_needed = foldr addExternal needed needed_prs
466 -- The 'needed' set contains the Ids that are needed by earlier
467 -- interface file emissions. If the Id isn't in this set, and isn't
468 -- exported, there's no need to emit anything
469 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
470 need_pr needed_set (id,rhs) = need_id needed_set id
472 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
473 -- The Id is needed; extend the needed set
474 -- with it and its dependents (free vars etc)
475 addExternal (id,rhs) needed
476 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
479 add_occ id needed | id `elemVarEnv` needed = needed
480 | otherwise = extendVarEnv needed id False
481 -- "False" because we don't know we need the Id's unfolding
482 -- Don't override existing bindings; we might have already set it to True
484 new_needed_ids = worker_ids `unionVarSet`
485 unfold_ids `unionVarSet`
489 dont_inline = isNeverActive (inlinePragInfo idinfo)
490 loop_breaker = isNonRuleLoopBreaker (occInfo idinfo)
491 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
492 spec_ids = specInfoFreeVars (specInfo idinfo)
493 worker_info = workerInfo idinfo
495 -- Stuff to do with the Id's unfolding
496 -- The simplifier has put an up-to-date unfolding
497 -- in the IdInfo, but the RHS will do just as well
498 unfolding = unfoldingInfo idinfo
499 rhs_is_small = not (neverUnfold unfolding)
501 -- We leave the unfolding there even if there is a worker
502 -- In GHCI the unfolding is used by importers
503 -- When writing an interface file, we omit the unfolding
504 -- if there is a worker
505 show_unfold = not bottoming_fn && -- Not necessary
508 rhs_is_small -- Small enough
510 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
511 | otherwise = emptyVarSet
513 worker_ids = case worker_info of
514 HasWorker work_id _ -> unitVarSet work_id
515 otherwise -> emptyVarSet
520 findExternalRules :: [CoreBind]
521 -> [CoreRule] -- Non-local rules (i.e. ones for imported fns)
522 -> IdEnv a -- Ids that are exported, so we need their rules
524 -- The complete rules are gotten by combining
525 -- a) the non-local rules
526 -- b) rules embedded in the top-level Ids
527 findExternalRules binds non_local_rules ext_ids
528 = filter (not . internal_rule) (non_local_rules ++ local_rules)
531 | id <- bindersOfBinds binds,
532 id `elemVarEnv` ext_ids,
533 rule <- idCoreRules id
537 = any internal_id (varSetElems (ruleLhsFreeIds rule))
538 -- Don't export a rule whose LHS mentions a locally-defined
539 -- Id that is completely internal (i.e. not visible to an
542 internal_id id = not (id `elemVarEnv` ext_ids)
547 %************************************************************************
549 \subsection{Step 2: top-level tidying}
551 %************************************************************************
555 -- TopTidyEnv: when tidying we need to know
556 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
557 -- These may have arisen because the
558 -- renamer read in an interface file mentioning M.$wf, say,
559 -- and assigned it unique r77. If, on this compilation, we've
560 -- invented an Id whose name is $wf (but with a different unique)
561 -- we want to rename it to have unique r77, so that we can do easy
562 -- comparisons with stuff from the interface file
564 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
567 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
569 tidyTopBinds :: HscEnv
572 -> IdEnv Bool -- Domain = Ids that should be external
573 -- True <=> their unfolding is external too
575 -> IO (TidyEnv, [CoreBind])
577 tidyTopBinds hsc_env mod type_env ext_ids binds
578 = tidy init_env binds
580 nc_var = hsc_NC hsc_env
582 -- We also make sure to avoid any exported binders. Consider
583 -- f{-u1-} = 1 -- Local decl
585 -- f{-u2-} = 2 -- Exported decl
587 -- The second exported decl must 'get' the name 'f', so we
588 -- have to put 'f' in the avoids list before we get to the first
589 -- decl. tidyTopId then does a no-op on exported binders.
590 init_env = (initTidyOccEnv avoids, emptyVarEnv)
591 avoids = [getOccName name | bndr <- typeEnvIds type_env,
592 let name = idName bndr,
594 -- In computing our "avoids" list, we must include
596 -- all things with global names (assigned once and for
597 -- all by the renamer)
598 -- since their names are "taken".
599 -- The type environment is a convenient source of such things.
601 this_pkg = thisPackage (hsc_dflags hsc_env)
603 tidy env [] = return (env, [])
604 tidy env (b:bs) = do { (env1, b') <- tidyTopBind this_pkg mod nc_var ext_ids env b
605 ; (env2, bs') <- tidy env1 bs
606 ; return (env2, b':bs') }
608 ------------------------
609 tidyTopBind :: PackageId
611 -> IORef NameCache -- For allocating new unique names
612 -> IdEnv Bool -- Domain = Ids that should be external
613 -- True <=> their unfolding is external too
614 -> TidyEnv -> CoreBind
615 -> IO (TidyEnv, CoreBind)
617 tidyTopBind this_pkg mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (NonRec bndr rhs)
618 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
619 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
620 ; subst2 = extendVarEnv subst1 bndr bndr'
621 ; tidy_env2 = (occ_env2, subst2) }
622 ; return (tidy_env2, NonRec bndr' rhs') }
624 caf_info = hasCafRefs this_pkg subst1 (idArity bndr) rhs
626 tidyTopBind this_pkg mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (Rec prs)
627 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
628 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
630 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
631 ; tidy_env2 = (occ_env2, subst2) }
632 ; return (tidy_env2, Rec prs') }
636 -- the CafInfo for a recursive group says whether *any* rhs in
637 -- the group may refer indirectly to a CAF (because then, they all do).
639 | or [ mayHaveCafRefs (hasCafRefs this_pkg subst1 (idArity bndr) rhs)
640 | (bndr,rhs) <- prs ] = MayHaveCafRefs
641 | otherwise = NoCafRefs
643 --------------------------------------------------------------------
645 -- This is where we set names to local/global based on whether they really are
646 -- externally visible (see comment at the top of this module). If the name
647 -- was previously local, we have to give it a unique occurrence name if
648 -- we intend to externalise it.
649 tidyTopNames mod nc_var ext_ids occ_env [] = return (occ_env, [])
650 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
651 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
652 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
653 ; return (occ_env2, name:names) }
655 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
656 -> Id -> IO (TidyOccEnv, Name)
657 tidyTopName mod nc_var ext_ids occ_env id
658 | global && internal = return (occ_env, localiseName name)
660 | global && external = return (occ_env, name)
661 -- Global names are assumed to have been allocated by the renamer,
662 -- so they already have the "right" unique
663 -- And it's a system-wide unique too
665 -- Now we get to the real reason that all this is in the IO Monad:
666 -- we have to update the name cache in a nice atomic fashion
668 | local && internal = do { nc <- readIORef nc_var
669 ; let (nc', new_local_name) = mk_new_local nc
670 ; writeIORef nc_var nc'
671 ; return (occ_env', new_local_name) }
672 -- Even local, internal names must get a unique occurrence, because
673 -- if we do -split-objs we externalise the name later, in the code generator
675 -- Similarly, we must make sure it has a system-wide Unique, because
676 -- the byte-code generator builds a system-wide Name->BCO symbol table
678 | local && external = do { nc <- readIORef nc_var
679 ; let (nc', new_external_name) = mk_new_external nc
680 ; writeIORef nc_var nc'
681 ; return (occ_env', new_external_name) }
684 external = id `elemVarEnv` ext_ids
685 global = isExternalName name
687 internal = not external
688 loc = nameSrcLoc name
690 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
692 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
694 (us1, us2) = splitUniqSupply (nsUniqs nc)
695 uniq = uniqFromSupply us1
697 mk_new_external nc = allocateGlobalBinder nc mod occ' loc
698 -- If we want to externalise a currently-local name, check
699 -- whether we have already assigned a unique for it.
700 -- If so, use it; if not, extend the table.
701 -- All this is done by allcoateGlobalBinder.
702 -- This is needed when *re*-compiling a module in GHCi; we must
703 -- use the same name for externally-visible things as we did before.
706 -----------------------------------------------------------
707 tidyTopPair :: VarEnv Bool
708 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
709 -- It is knot-tied: don't look at it!
712 -> (Id, CoreExpr) -- Binder and RHS before tidying
714 -- This function is the heart of Step 2
715 -- The rec_tidy_env is the one to use for the IdInfo
716 -- It's necessary because when we are dealing with a recursive
717 -- group, a variable late in the group might be mentioned
718 -- in the IdInfo of one early in the group
720 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
721 | isGlobalId bndr -- Injected binding for record selector, etc
722 = (bndr, tidyExpr rhs_tidy_env rhs)
726 bndr' = mkVanillaGlobal name' ty' idinfo'
727 ty' = tidyTopType (idType bndr)
728 rhs' = tidyExpr rhs_tidy_env rhs
729 idinfo' = tidyTopIdInfo rhs_tidy_env (isJust maybe_external)
730 (idInfo bndr) unfold_info arity
733 -- Expose an unfolding if ext_ids tells us to
734 -- Remember that ext_ids maps an Id to a Bool:
735 -- True to show the unfolding, False to hide it
736 maybe_external = lookupVarEnv ext_ids bndr
737 show_unfold = maybe_external `orElse` False
738 unfold_info | show_unfold = mkTopUnfolding rhs'
739 | otherwise = noUnfolding
741 -- Usually the Id will have an accurate arity on it, because
742 -- the simplifier has just run, but not always.
743 -- One case I found was when the last thing the simplifier
744 -- did was to let-bind a non-atomic argument and then float
745 -- it to the top level. So it seems more robust just to
747 arity = exprArity rhs
750 -- tidyTopIdInfo creates the final IdInfo for top-level
751 -- binders. There are two delicate pieces:
753 -- * Arity. After CoreTidy, this arity must not change any more.
754 -- Indeed, CorePrep must eta expand where necessary to make
755 -- the manifest arity equal to the claimed arity.
757 -- * CAF info. This must also remain valid through to code generation.
758 -- We add the info here so that it propagates to all
759 -- occurrences of the binders in RHSs, and hence to occurrences in
760 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
761 -- CoreToStg makes use of this when constructing SRTs.
763 tidyTopIdInfo tidy_env is_external idinfo unfold_info arity caf_info
764 | not is_external -- For internal Ids (not externally visible)
765 = vanillaIdInfo -- we only need enough info for code generation
766 -- Arity and strictness info are enough;
767 -- c.f. CoreTidy.tidyLetBndr
768 `setCafInfo` caf_info
770 `setAllStrictnessInfo` newStrictnessInfo idinfo
772 | otherwise -- Externally-visible Ids get the whole lot
774 `setCafInfo` caf_info
776 `setAllStrictnessInfo` newStrictnessInfo idinfo
777 `setInlinePragInfo` inlinePragInfo idinfo
778 `setUnfoldingInfo` unfold_info
779 `setWorkerInfo` tidyWorker tidy_env (workerInfo idinfo)
780 -- NB: we throw away the Rules
781 -- They have already been extracted by findExternalRules
785 ------------ Worker --------------
786 tidyWorker tidy_env (HasWorker work_id wrap_arity)
787 = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
788 tidyWorker tidy_env other
792 %************************************************************************
794 \subsection{Figuring out CafInfo for an expression}
796 %************************************************************************
798 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
799 We mark such things as `MayHaveCafRefs' because this information is
800 used to decide whether a particular closure needs to be referenced
803 There are two reasons for setting MayHaveCafRefs:
804 a) The RHS is a CAF: a top-level updatable thunk.
805 b) The RHS refers to something that MayHaveCafRefs
807 Possible improvement: In an effort to keep the number of CAFs (and
808 hence the size of the SRTs) down, we could also look at the expression and
809 decide whether it requires a small bounded amount of heap, so we can ignore
810 it as a CAF. In these cases however, we would need to use an additional
811 CAF list to keep track of non-collectable CAFs.
814 hasCafRefs :: PackageId -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
815 hasCafRefs this_pkg p arity expr
816 | is_caf || mentions_cafs
818 | otherwise = NoCafRefs
820 mentions_cafs = isFastTrue (cafRefs p expr)
821 is_caf = not (arity > 0 || rhsIsStatic this_pkg expr)
823 -- NB. we pass in the arity of the expression, which is expected
824 -- to be calculated by exprArity. This is because exprArity
825 -- knows how much eta expansion is going to be done by
826 -- CorePrep later on, and we don't want to duplicate that
827 -- knowledge in rhsIsStatic below.
830 -- imported Ids first:
831 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
832 -- now Ids local to this module:
834 case lookupVarEnv p id of
835 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
836 Nothing -> fastBool False
838 cafRefs p (Lit l) = fastBool False
839 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
840 cafRefs p (Lam x e) = cafRefs p e
841 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
842 cafRefs p (Case e bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
843 cafRefs p (Note n e) = cafRefs p e
844 cafRefs p (Cast e co) = cafRefs p e
845 cafRefs p (Type t) = fastBool False
847 cafRefss p [] = fastBool False
848 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
850 -- hack for lazy-or over FastBool.
851 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))