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
26 import IdInfo {- loads of stuff -}
27 import InstEnv ( Instance, DFunId, instanceDFunId, setInstanceDFunId )
28 import NewDemand ( isBottomingSig, topSig )
29 import BasicTypes ( Arity, isNeverActive, isNonRuleLoopBreaker )
30 import Name ( Name, getOccName, nameOccName, mkInternalName,
31 localiseName, isExternalName, nameSrcLoc,
32 isWiredInName, getName
34 import NameSet ( NameSet, elemNameSet )
35 import IfaceEnv ( allocateGlobalBinder )
36 import NameEnv ( filterNameEnv, mapNameEnv )
37 import OccName ( TidyOccEnv, initTidyOccEnv, tidyOccName )
38 import Type ( tidyTopType )
39 import TcType ( isFFITy )
40 import DataCon ( dataConName, dataConFieldLabels, dataConWrapId_maybe )
41 import TyCon ( TyCon, makeTyConAbstract, tyConDataCons, isNewTyCon,
42 newTyConRep, tyConSelIds, isAlgTyCon,
43 isEnumerationTyCon, isOpenTyCon )
44 import Class ( classSelIds )
45 import Module ( Module )
47 import Maybes ( orElse, mapCatMaybes )
48 import ErrUtils ( showPass, dumpIfSet_core )
49 import PackageConfig ( PackageId )
50 import UniqSupply ( splitUniqSupply, uniqFromSupply )
52 import FastTypes hiding ( fastOr )
54 import Data.List ( partition )
55 import Data.Maybe ( isJust )
56 import Data.IORef ( IORef, readIORef, writeIORef )
60 Constructing the TypeEnv, Instances, Rules from which the ModIface is
61 constructed, and which goes on to subsequent modules in --make mode.
63 Most of the interface file is obtained simply by serialising the
64 TypeEnv. One important consequence is that if the *interface file*
65 has pragma info if and only if the final TypeEnv does. This is not so
66 important for *this* module, but it's essential for ghc --make:
67 subsequent compilations must not see (e.g.) the arity if the interface
68 file does not contain arity If they do, they'll exploit the arity;
69 then the arity might change, but the iface file doesn't change =>
70 recompilation does not happen => disaster.
72 For data types, the final TypeEnv will have a TyThing for the TyCon,
73 plus one for each DataCon; the interface file will contain just one
74 data type declaration, but it is de-serialised back into a collection
77 %************************************************************************
81 %************************************************************************
84 Plan A: mkBootModDetails: omit pragmas, make interfaces small
85 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
88 * Drop all WiredIn things from the TypeEnv
89 (we never want them in interface files)
91 * Retain all TyCons and Classes in the TypeEnv, to avoid
92 having to find which ones are mentioned in the
95 * Trim off the constructors of non-exported TyCons, both
96 from the TyCon and from the TypeEnv
98 * Drop non-exported Ids from the TypeEnv
100 * Tidy the types of the DFunIds of Instances,
101 make them into GlobalIds, (they already have External Names)
102 and add them to the TypeEnv
104 * Tidy the types of the (exported) Ids in the TypeEnv,
105 make them into GlobalIds (they already have External Names)
107 * Drop rules altogether
109 * Tidy the bindings, to ensure that the Caf and Arity
110 information is correct for each top-level binder; the
111 code generator needs it. And to ensure that local names have
112 distinct OccNames in case of object-file splitting
115 mkBootModDetails :: HscEnv -> ModGuts -> IO ModDetails
116 -- This is Plan A: make a small type env when typechecking only,
117 -- or when compiling a hs-boot file, or simply when not using -O
119 -- We don't look at the bindings at all -- there aren't any
122 mkBootModDetails hsc_env (ModGuts { mg_module = mod
123 , mg_exports = exports
124 , mg_types = type_env
126 , mg_fam_insts = fam_insts })
127 = do { let dflags = hsc_dflags hsc_env
128 ; showPass dflags "Tidy [hoot] type env"
130 ; let { insts' = tidyInstances tidyExternalId insts
131 ; type_env1 = filterNameEnv (not . isWiredInThing) type_env
132 ; type_env2 = mapNameEnv tidyBootThing type_env1
133 ; type_env' = extendTypeEnvWithIds type_env2
134 (map instanceDFunId insts')
136 ; return (ModDetails { md_types = type_env'
138 , md_fam_insts = fam_insts
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,
238 mg_insts = insts, mg_fam_insts = fam_insts,
240 mg_rules = imp_rules,
241 mg_dir_imps = dir_imps, mg_deps = deps,
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 mod type_env ext_ids
263 ; let { export_set = availsToNameSet exports
264 ; tidy_type_env = tidyTypeEnv omit_prags export_set type_env
266 ; tidy_insts = tidyInstances (lookup_dfun tidy_type_env) insts
267 -- A DFunId will have a binding in tidy_binds, and so
268 -- will now be in final_env, replete with IdInfo
269 -- Its name will be unchanged since it was born, but
270 -- we want Global, IdInfo-rich (or not) DFunId in the
273 ; tidy_rules = tidyRules tidy_env ext_rules
274 -- You might worry that the tidy_env contains IdInfo-rich stuff
275 -- and indeed it does, but if omit_prags is on, ext_rules is
278 ; implicit_binds = getImplicitBinds type_env
279 ; all_tidy_binds = implicit_binds ++ tidy_binds
280 ; alg_tycons = filter isAlgTyCon (typeEnvTyCons type_env)
283 ; endPass dflags "Tidy Core" Opt_D_dump_simpl all_tidy_binds
284 ; dumpIfSet_core dflags Opt_D_dump_simpl
286 (pprRules tidy_rules)
288 ; return (CgGuts { cg_module = mod,
289 cg_tycons = alg_tycons,
290 cg_binds = all_tidy_binds,
291 cg_dir_imps = dir_imps,
292 cg_foreign = foreign_stubs,
293 cg_dep_pkgs = dep_pkgs deps },
295 ModDetails { md_types = tidy_type_env,
296 md_rules = tidy_rules,
297 md_insts = tidy_insts,
298 md_fam_insts = fam_insts,
299 md_exports = exports })
302 lookup_dfun type_env dfun_id
303 = case lookupTypeEnv type_env (idName dfun_id) of
304 Just (AnId dfun_id') -> dfun_id'
305 other -> pprPanic "lookup_dfun" (ppr dfun_id)
307 tidyTypeEnv :: Bool -> NameSet -> TypeEnv -> [CoreBind] -> TypeEnv
309 -- The competed type environment is gotten from
310 -- Dropping any wired-in things, and then
311 -- a) keeping the types and classes
312 -- b) removing all Ids,
313 -- c) adding Ids with correct IdInfo, including unfoldings,
314 -- gotten from the bindings
315 -- From (c) we keep only those Ids with External names;
316 -- the CoreTidy pass makes sure these are all and only
317 -- the externally-accessible ones
318 -- This truncates the type environment to include only the
319 -- exported Ids and things needed from them, which saves space
321 tidyTypeEnv omit_prags exports type_env tidy_binds
322 = let type_env1 = filterNameEnv keep_it type_env
323 type_env2 = extendTypeEnvWithIds type_env1 final_ids
324 type_env3 | omit_prags = mapNameEnv trim_thing type_env2
325 | otherwise = type_env2
329 final_ids = [ id | id <- bindersOfBinds tidy_binds,
330 isExternalName (idName id)]
332 -- We keep GlobalIds, because they won't appear
333 -- in the bindings from which final_ids are derived!
334 -- (The bindings bind LocalIds.)
335 keep_it thing | isWiredInThing thing = False
336 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
337 keep_it other = True -- Keep all TyCons, DataCons, and Classes
341 ATyCon tc | mustExposeTyCon exports tc -> thing
342 | otherwise -> ATyCon (makeTyConAbstract tc)
344 AnId id | isImplicitId id -> thing
345 | otherwise -> AnId (id `setIdInfo` vanillaIdInfo)
349 mustExposeTyCon :: NameSet -- Exports
350 -> TyCon -- The tycon
351 -> Bool -- Can its rep be hidden?
352 -- We are compiling without -O, and thus trying to write as little as
353 -- possible into the interface file. But we must expose the details of
354 -- any data types whose constructors or fields are exported
355 mustExposeTyCon exports tc
356 | not (isAlgTyCon tc) -- Synonyms
358 | isEnumerationTyCon tc -- For an enumeration, exposing the constructors
359 = True -- won't lead to the need for further exposure
360 -- (This includes data types with no constructors.)
361 | isOpenTyCon tc -- open type family
363 | otherwise -- Newtype, datatype
364 = any exported_con (tyConDataCons tc)
365 -- Expose rep if any datacon or field is exported
367 || (isNewTyCon tc && isFFITy (snd (newTyConRep tc)))
368 -- Expose the rep for newtypes if the rep is an FFI type.
369 -- For a very annoying reason. 'Foreign import' is meant to
370 -- be able to look through newtypes transparently, but it
371 -- can only do that if it can "see" the newtype representation
373 exported_con con = any (`elemNameSet` exports)
374 (dataConName con : dataConFieldLabels con)
376 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
377 tidyInstances tidy_dfun ispecs
380 tidy ispec = setInstanceDFunId ispec $
381 tidy_dfun (instanceDFunId ispec)
383 getImplicitBinds :: TypeEnv -> [CoreBind]
384 getImplicitBinds type_env
385 = map get_defn (concatMap implicit_con_ids (typeEnvTyCons type_env)
386 ++ concatMap other_implicit_ids (typeEnvElts type_env))
387 -- Put the constructor wrappers first, because
388 -- other implicit bindings (notably the fromT functions arising
389 -- from generics) use the constructor wrappers. At least that's
390 -- what External Core likes
392 implicit_con_ids tc = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
394 other_implicit_ids (ATyCon tc) = filter (not . isNaughtyRecordSelector) (tyConSelIds tc)
395 -- The "naughty" ones are not real functions at all
396 -- They are there just so we can get decent error messages
397 -- See Note [Naughty record selectors] in MkId.lhs
398 other_implicit_ids (AClass cl) = classSelIds cl
399 other_implicit_ids other = []
401 get_defn :: Id -> CoreBind
402 get_defn id = NonRec id (tidyExpr emptyTidyEnv rhs)
404 rhs = unfoldingTemplate (idUnfolding id)
405 -- Don't forget to tidy the body ! Otherwise you get silly things like
406 -- \ tpl -> case tpl of tpl -> (tpl,tpl) -> tpl
410 %************************************************************************
412 \subsection{Step 1: finding externals}
414 %************************************************************************
417 findExternalIds :: Bool
419 -> IdEnv Bool -- In domain => external
420 -- Range = True <=> show unfolding
421 -- Step 1 from the notes above
422 findExternalIds omit_prags binds
424 = mkVarEnv [ (id,False) | id <- bindersOfBinds binds, isExportedId id ]
427 = foldr find emptyVarEnv binds
429 find (NonRec id rhs) needed
430 | need_id needed id = addExternal (id,rhs) needed
432 find (Rec prs) needed = find_prs prs needed
434 -- For a recursive group we have to look for a fixed point
436 | null needed_prs = needed
437 | otherwise = find_prs other_prs new_needed
439 (needed_prs, other_prs) = partition (need_pr needed) prs
440 new_needed = foldr addExternal needed needed_prs
442 -- The 'needed' set contains the Ids that are needed by earlier
443 -- interface file emissions. If the Id isn't in this set, and isn't
444 -- exported, there's no need to emit anything
445 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
446 need_pr needed_set (id,rhs) = need_id needed_set id
448 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
449 -- The Id is needed; extend the needed set
450 -- with it and its dependents (free vars etc)
451 addExternal (id,rhs) needed
452 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
455 add_occ id needed | id `elemVarEnv` needed = needed
456 | otherwise = extendVarEnv needed id False
457 -- "False" because we don't know we need the Id's unfolding
458 -- Don't override existing bindings; we might have already set it to True
460 new_needed_ids = worker_ids `unionVarSet`
461 unfold_ids `unionVarSet`
465 dont_inline = isNeverActive (inlinePragInfo idinfo)
466 loop_breaker = isNonRuleLoopBreaker (occInfo idinfo)
467 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
468 spec_ids = specInfoFreeVars (specInfo idinfo)
469 worker_info = workerInfo idinfo
471 -- Stuff to do with the Id's unfolding
472 -- The simplifier has put an up-to-date unfolding
473 -- in the IdInfo, but the RHS will do just as well
474 unfolding = unfoldingInfo idinfo
475 rhs_is_small = not (neverUnfold unfolding)
477 -- We leave the unfolding there even if there is a worker
478 -- In GHCI the unfolding is used by importers
479 -- When writing an interface file, we omit the unfolding
480 -- if there is a worker
481 show_unfold = not bottoming_fn && -- Not necessary
484 rhs_is_small -- Small enough
486 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
487 | otherwise = emptyVarSet
489 worker_ids = case worker_info of
490 HasWorker work_id _ -> unitVarSet work_id
491 otherwise -> emptyVarSet
496 findExternalRules :: [CoreBind]
497 -> [CoreRule] -- Non-local rules (i.e. ones for imported fns)
498 -> IdEnv a -- Ids that are exported, so we need their rules
500 -- The complete rules are gotten by combining
501 -- a) the non-local rules
502 -- b) rules embedded in the top-level Ids
503 findExternalRules binds non_local_rules ext_ids
504 = filter (not . internal_rule) (non_local_rules ++ local_rules)
507 | id <- bindersOfBinds binds,
508 id `elemVarEnv` ext_ids,
509 rule <- idCoreRules id
513 = any internal_id (varSetElems (ruleLhsFreeIds rule))
514 -- Don't export a rule whose LHS mentions a locally-defined
515 -- Id that is completely internal (i.e. not visible to an
518 internal_id id = not (id `elemVarEnv` ext_ids)
523 %************************************************************************
525 \subsection{Step 2: top-level tidying}
527 %************************************************************************
531 -- TopTidyEnv: when tidying we need to know
532 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
533 -- These may have arisen because the
534 -- renamer read in an interface file mentioning M.$wf, say,
535 -- and assigned it unique r77. If, on this compilation, we've
536 -- invented an Id whose name is $wf (but with a different unique)
537 -- we want to rename it to have unique r77, so that we can do easy
538 -- comparisons with stuff from the interface file
540 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
543 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
545 tidyTopBinds :: HscEnv
548 -> IdEnv Bool -- Domain = Ids that should be external
549 -- True <=> their unfolding is external too
551 -> IO (TidyEnv, [CoreBind])
553 tidyTopBinds hsc_env mod type_env ext_ids binds
554 = tidy init_env binds
556 nc_var = hsc_NC hsc_env
558 -- We also make sure to avoid any exported binders. Consider
559 -- f{-u1-} = 1 -- Local decl
561 -- f{-u2-} = 2 -- Exported decl
563 -- The second exported decl must 'get' the name 'f', so we
564 -- have to put 'f' in the avoids list before we get to the first
565 -- decl. tidyTopId then does a no-op on exported binders.
566 init_env = (initTidyOccEnv avoids, emptyVarEnv)
567 avoids = [getOccName name | bndr <- typeEnvIds type_env,
568 let name = idName bndr,
570 -- In computing our "avoids" list, we must include
572 -- all things with global names (assigned once and for
573 -- all by the renamer)
574 -- since their names are "taken".
575 -- The type environment is a convenient source of such things.
577 this_pkg = thisPackage (hsc_dflags hsc_env)
579 tidy env [] = return (env, [])
580 tidy env (b:bs) = do { (env1, b') <- tidyTopBind this_pkg mod nc_var ext_ids env b
581 ; (env2, bs') <- tidy env1 bs
582 ; return (env2, b':bs') }
584 ------------------------
585 tidyTopBind :: PackageId
587 -> IORef NameCache -- For allocating new unique names
588 -> IdEnv Bool -- Domain = Ids that should be external
589 -- True <=> their unfolding is external too
590 -> TidyEnv -> CoreBind
591 -> IO (TidyEnv, CoreBind)
593 tidyTopBind this_pkg mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (NonRec bndr rhs)
594 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
595 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
596 ; subst2 = extendVarEnv subst1 bndr bndr'
597 ; tidy_env2 = (occ_env2, subst2) }
598 ; return (tidy_env2, NonRec bndr' rhs') }
600 caf_info = hasCafRefs this_pkg subst1 (idArity bndr) rhs
602 tidyTopBind this_pkg mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (Rec prs)
603 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
604 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
606 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
607 ; tidy_env2 = (occ_env2, subst2) }
608 ; return (tidy_env2, Rec prs') }
612 -- the CafInfo for a recursive group says whether *any* rhs in
613 -- the group may refer indirectly to a CAF (because then, they all do).
615 | or [ mayHaveCafRefs (hasCafRefs this_pkg subst1 (idArity bndr) rhs)
616 | (bndr,rhs) <- prs ] = MayHaveCafRefs
617 | otherwise = NoCafRefs
619 --------------------------------------------------------------------
621 -- This is where we set names to local/global based on whether they really are
622 -- externally visible (see comment at the top of this module). If the name
623 -- was previously local, we have to give it a unique occurrence name if
624 -- we intend to externalise it.
625 tidyTopNames mod nc_var ext_ids occ_env [] = return (occ_env, [])
626 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
627 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
628 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
629 ; return (occ_env2, name:names) }
631 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
632 -> Id -> IO (TidyOccEnv, Name)
633 tidyTopName mod nc_var ext_ids occ_env id
634 | global && internal = return (occ_env, localiseName name)
636 | global && external = return (occ_env, name)
637 -- Global names are assumed to have been allocated by the renamer,
638 -- so they already have the "right" unique
639 -- And it's a system-wide unique too
641 -- Now we get to the real reason that all this is in the IO Monad:
642 -- we have to update the name cache in a nice atomic fashion
644 | local && internal = do { nc <- readIORef nc_var
645 ; let (nc', new_local_name) = mk_new_local nc
646 ; writeIORef nc_var nc'
647 ; return (occ_env', new_local_name) }
648 -- Even local, internal names must get a unique occurrence, because
649 -- if we do -split-objs we externalise the name later, in the code generator
651 -- Similarly, we must make sure it has a system-wide Unique, because
652 -- the byte-code generator builds a system-wide Name->BCO symbol table
654 | local && external = do { nc <- readIORef nc_var
655 ; let (nc', new_external_name) = mk_new_external nc
656 ; writeIORef nc_var nc'
657 ; return (occ_env', new_external_name) }
660 external = id `elemVarEnv` ext_ids
661 global = isExternalName name
663 internal = not external
664 loc = nameSrcLoc name
666 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
668 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
670 (us1, us2) = splitUniqSupply (nsUniqs nc)
671 uniq = uniqFromSupply us1
673 mk_new_external nc = allocateGlobalBinder nc mod occ' loc
674 -- If we want to externalise a currently-local name, check
675 -- whether we have already assigned a unique for it.
676 -- If so, use it; if not, extend the table.
677 -- All this is done by allcoateGlobalBinder.
678 -- This is needed when *re*-compiling a module in GHCi; we must
679 -- use the same name for externally-visible things as we did before.
682 -----------------------------------------------------------
683 tidyTopPair :: VarEnv Bool
684 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
685 -- It is knot-tied: don't look at it!
688 -> (Id, CoreExpr) -- Binder and RHS before tidying
690 -- This function is the heart of Step 2
691 -- The rec_tidy_env is the one to use for the IdInfo
692 -- It's necessary because when we are dealing with a recursive
693 -- group, a variable late in the group might be mentioned
694 -- in the IdInfo of one early in the group
696 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
697 | isGlobalId bndr -- Injected binding for record selector, etc
698 = (bndr, tidyExpr rhs_tidy_env rhs)
702 bndr' = mkVanillaGlobal name' ty' idinfo'
703 ty' = tidyTopType (idType bndr)
704 rhs' = tidyExpr rhs_tidy_env rhs
705 idinfo' = tidyTopIdInfo rhs_tidy_env (isJust maybe_external)
706 (idInfo bndr) unfold_info arity
709 -- Expose an unfolding if ext_ids tells us to
710 -- Remember that ext_ids maps an Id to a Bool:
711 -- True to show the unfolding, False to hide it
712 maybe_external = lookupVarEnv ext_ids bndr
713 show_unfold = maybe_external `orElse` False
714 unfold_info | show_unfold = mkTopUnfolding rhs'
715 | otherwise = noUnfolding
717 -- Usually the Id will have an accurate arity on it, because
718 -- the simplifier has just run, but not always.
719 -- One case I found was when the last thing the simplifier
720 -- did was to let-bind a non-atomic argument and then float
721 -- it to the top level. So it seems more robust just to
723 arity = exprArity rhs
726 -- tidyTopIdInfo creates the final IdInfo for top-level
727 -- binders. There are two delicate pieces:
729 -- * Arity. After CoreTidy, this arity must not change any more.
730 -- Indeed, CorePrep must eta expand where necessary to make
731 -- the manifest arity equal to the claimed arity.
733 -- * CAF info. This must also remain valid through to code generation.
734 -- We add the info here so that it propagates to all
735 -- occurrences of the binders in RHSs, and hence to occurrences in
736 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
737 -- CoreToStg makes use of this when constructing SRTs.
739 tidyTopIdInfo tidy_env is_external idinfo unfold_info arity caf_info
740 | not is_external -- For internal Ids (not externally visible)
741 = vanillaIdInfo -- we only need enough info for code generation
742 -- Arity and strictness info are enough;
743 -- c.f. CoreTidy.tidyLetBndr
744 `setCafInfo` caf_info
746 `setAllStrictnessInfo` newStrictnessInfo idinfo
748 | otherwise -- Externally-visible Ids get the whole lot
750 `setCafInfo` caf_info
752 `setAllStrictnessInfo` newStrictnessInfo idinfo
753 `setInlinePragInfo` inlinePragInfo idinfo
754 `setUnfoldingInfo` unfold_info
755 `setWorkerInfo` tidyWorker tidy_env (workerInfo idinfo)
756 -- NB: we throw away the Rules
757 -- They have already been extracted by findExternalRules
761 ------------ Worker --------------
762 tidyWorker tidy_env (HasWorker work_id wrap_arity)
763 = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
764 tidyWorker tidy_env other
768 %************************************************************************
770 \subsection{Figuring out CafInfo for an expression}
772 %************************************************************************
774 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
775 We mark such things as `MayHaveCafRefs' because this information is
776 used to decide whether a particular closure needs to be referenced
779 There are two reasons for setting MayHaveCafRefs:
780 a) The RHS is a CAF: a top-level updatable thunk.
781 b) The RHS refers to something that MayHaveCafRefs
783 Possible improvement: In an effort to keep the number of CAFs (and
784 hence the size of the SRTs) down, we could also look at the expression and
785 decide whether it requires a small bounded amount of heap, so we can ignore
786 it as a CAF. In these cases however, we would need to use an additional
787 CAF list to keep track of non-collectable CAFs.
790 hasCafRefs :: PackageId -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
791 hasCafRefs this_pkg p arity expr
792 | is_caf || mentions_cafs = MayHaveCafRefs
793 | otherwise = NoCafRefs
795 mentions_cafs = isFastTrue (cafRefs p expr)
796 is_caf = not (arity > 0 || rhsIsStatic this_pkg expr)
797 -- NB. we pass in the arity of the expression, which is expected
798 -- to be calculated by exprArity. This is because exprArity
799 -- knows how much eta expansion is going to be done by
800 -- CorePrep later on, and we don't want to duplicate that
801 -- knowledge in rhsIsStatic below.
804 -- imported Ids first:
805 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
806 -- now Ids local to this module:
808 case lookupVarEnv p id of
809 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
810 Nothing -> fastBool False
812 cafRefs p (Lit l) = fastBool False
813 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
814 cafRefs p (Lam x e) = cafRefs p e
815 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
816 cafRefs p (Case e bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
817 cafRefs p (Note n e) = cafRefs p e
818 cafRefs p (Cast e co) = cafRefs p e
819 cafRefs p (Type t) = fastBool False
821 cafRefss p [] = fastBool False
822 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
824 -- hack for lazy-or over FastBool.
825 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))