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 )
30 import Name ( Name, getOccName, nameOccName, mkInternalName,
31 localiseName, isExternalName, nameSrcLoc, nameParent_maybe,
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 )
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 PackageConfig ( PackageId )
54 import UniqSupply ( splitUniqSupply, uniqFromSupply )
55 import List ( partition )
56 import Maybe ( isJust )
58 import DATA_IOREF ( IORef, readIORef, writeIORef )
59 import FastTypes hiding ( fastOr )
63 Constructing the TypeEnv, Instances, Rules from which the ModIface is
64 constructed, and which goes on to subsequent modules in --make mode.
66 Most of the interface file is obtained simply by serialising the
67 TypeEnv. One important consequence is that if the *interface file*
68 has pragma info if and only if the final TypeEnv does. This is not so
69 important for *this* module, but it's essential for ghc --make:
70 subsequent compilations must not see (e.g.) the arity if the interface
71 file does not contain arity If they do, they'll exploit the arity;
72 then the arity might change, but the iface file doesn't change =>
73 recompilation does not happen => disaster.
75 For data types, the final TypeEnv will have a TyThing for the TyCon,
76 plus one for each DataCon; the interface file will contain just one
77 data type declaration, but it is de-serialised back into a collection
80 %************************************************************************
84 %************************************************************************
87 Plan A: mkBootModDetails: omit pragmas, make interfaces small
88 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
91 * Drop all WiredIn things from the TypeEnv
92 (we never want them in interface files)
94 * Retain all TyCons and Classes in the TypeEnv, to avoid
95 having to find which ones are mentioned in the
98 * Trim off the constructors of non-exported TyCons, both
99 from the TyCon and from the TypeEnv
101 * Drop non-exported Ids from the TypeEnv
103 * Tidy the types of the DFunIds of Instances,
104 make them into GlobalIds, (they already have External Names)
105 and add them to the TypeEnv
107 * Tidy the types of the (exported) Ids in the TypeEnv,
108 make them into GlobalIds (they already have External Names)
110 * Drop rules altogether
112 * Tidy the bindings, to ensure that the Caf and Arity
113 information is correct for each top-level binder; the
114 code generator needs it. And to ensure that local names have
115 distinct OccNames in case of object-file splitting
118 mkBootModDetails :: HscEnv -> ModGuts -> IO ModDetails
119 -- This is Plan A: make a small type env when typechecking only,
120 -- or when compiling a hs-boot file, or simply when not using -O
122 -- We don't look at the bindings at all -- there aren't any
125 mkBootModDetails hsc_env (ModGuts { mg_module = mod,
126 mg_exports = exports,
129 = do { let dflags = hsc_dflags hsc_env
130 ; showPass dflags "Tidy [hoot] type env"
132 ; let { ispecs' = tidyInstances tidyExternalId ispecs
133 ; type_env1 = filterNameEnv (not . isWiredInThing) type_env
134 ; type_env2 = mapNameEnv tidyBootThing type_env1
135 ; type_env' = extendTypeEnvWithIds type_env2
136 (map instanceDFunId ispecs')
138 ; return (ModDetails { md_types = type_env',
141 md_exports = exports })
145 isWiredInThing :: TyThing -> Bool
146 isWiredInThing thing = isWiredInName (getName thing)
148 tidyBootThing :: TyThing -> TyThing
149 -- Just externalise the Ids; keep everything
150 tidyBootThing (AnId id) | isLocalId id = AnId (tidyExternalId id)
151 tidyBootThing thing = thing
153 tidyExternalId :: Id -> Id
154 -- Takes an LocalId with an External Name,
155 -- makes it into a GlobalId with VanillaIdInfo, and tidies its type
156 -- (NB: vanillaIdInfo makes a conservative assumption about Caf-hood.)
158 = ASSERT2( isLocalId id && isExternalName (idName id), ppr id )
159 mkVanillaGlobal (idName id) (tidyTopType (idType id)) vanillaIdInfo
163 %************************************************************************
165 Plan B: tidy bindings, make TypeEnv full of IdInfo
167 %************************************************************************
169 Plan B: include pragmas, make interfaces
170 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
171 * Figure out which Ids are externally visible
173 * Tidy the bindings, externalising appropriate Ids
175 * Drop all Ids from the TypeEnv, and add all the External Ids from
176 the bindings. (This adds their IdInfo to the TypeEnv; and adds
177 floated-out Ids that weren't even in the TypeEnv before.)
179 Step 1: Figure out external Ids
180 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
181 First we figure out which Ids are "external" Ids. An
182 "external" Id is one that is visible from outside the compilation
184 a) the user exported ones
185 b) ones mentioned in the unfoldings, workers,
186 or rules of externally-visible ones
187 This exercise takes a sweep of the bindings bottom to top. Actually,
188 in Step 2 we're also going to need to know which Ids should be
189 exported with their unfoldings, so we produce not an IdSet but an
193 Step 2: Tidy the program
194 ~~~~~~~~~~~~~~~~~~~~~~~~
195 Next we traverse the bindings top to bottom. For each *top-level*
198 1. Make it into a GlobalId; its IdDetails becomes VanillaGlobal,
199 reflecting the fact that from now on we regard it as a global,
202 2. Give it a system-wide Unique.
203 [Even non-exported things need system-wide Uniques because the
204 byte-code generator builds a single Name->BCO symbol table.]
206 We use the NameCache kept in the HscEnv as the
207 source of such system-wide uniques.
209 For external Ids, use the original-name cache in the NameCache
210 to ensure that the unique assigned is the same as the Id had
211 in any previous compilation run.
213 3. If it's an external Id, make it have a External Name, otherwise
214 make it have an Internal Name.
215 This is used by the code generator to decide whether
216 to make the label externally visible
218 4. Give external Ids a "tidy" OccName. This means
219 we can print them in interface files without confusing
220 "x" (unique 5) with "x" (unique 10).
222 5. Give it its UTTERLY FINAL IdInfo; in ptic,
223 * its unfolding, if it should have one
225 * its arity, computed from the number of visible lambdas
227 * its CAF info, computed from what is free in its RHS
230 Finally, substitute these new top-level binders consistently
231 throughout, including in unfoldings. We also tidy binders in
232 RHSs, so that they print nicely in interfaces.
235 tidyProgram :: HscEnv -> ModGuts -> IO (CgGuts, ModDetails)
237 mod_impl@(ModGuts { mg_module = mod, mg_exports = exports,
238 mg_types = type_env, mg_insts = insts_tc,
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 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_dep_pkgs = dep_pkgs deps },
290 ModDetails { md_types = tidy_type_env,
291 md_rules = tidy_rules,
292 md_insts = tidy_ispecs,
293 md_exports = exports })
296 lookup_dfun type_env dfun_id
297 = case lookupTypeEnv type_env (idName dfun_id) of
298 Just (AnId dfun_id') -> dfun_id'
299 other -> pprPanic "lookup_dfun" (ppr dfun_id)
301 tidyTypeEnv :: Bool -> NameSet -> TypeEnv -> [CoreBind] -> TypeEnv
303 -- The competed type environment is gotten from
304 -- Dropping any wired-in things, and then
305 -- a) keeping the types and classes
306 -- b) removing all Ids,
307 -- c) adding Ids with correct IdInfo, including unfoldings,
308 -- gotten from the bindings
309 -- From (c) we keep only those Ids with External names;
310 -- the CoreTidy pass makes sure these are all and only
311 -- the externally-accessible ones
312 -- This truncates the type environment to include only the
313 -- exported Ids and things needed from them, which saves space
315 tidyTypeEnv omit_prags exports type_env tidy_binds
316 = let type_env1 = filterNameEnv keep_it type_env
317 type_env2 = extendTypeEnvWithIds type_env1 final_ids
318 type_env3 | omit_prags = mapNameEnv trim_thing type_env2
319 | otherwise = type_env2
323 final_ids = [ id | id <- bindersOfBinds tidy_binds,
324 isExternalName (idName id)]
326 -- We keep GlobalIds, because they won't appear
327 -- in the bindings from which final_ids are derived!
328 -- (The bindings bind LocalIds.)
329 keep_it thing | isWiredInThing thing = False
330 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
331 keep_it other = True -- Keep all TyCons, DataCons, and Classes
335 ATyCon tc | mustExposeTyCon exports tc -> thing
336 | otherwise -> ATyCon (makeTyConAbstract tc)
338 AnId id | isImplicitId id -> thing
339 | otherwise -> AnId (id `setIdInfo` vanillaIdInfo)
343 mustExposeTyCon :: NameSet -- Exports
344 -> TyCon -- The tycon
345 -> Bool -- Can its rep be hidden?
346 -- We are compiling without -O, and thus trying to write as little as
347 -- possible into the interface file. But we must expose the details of
348 -- any data types whose constructors or fields are exported
349 mustExposeTyCon exports tc
350 | not (isAlgTyCon tc) -- Synonyms
352 | isEnumerationTyCon tc -- For an enumeration, exposing the constructors
353 = True -- won't lead to the need for further exposure
354 -- (This includes data types with no constructors.)
355 | isOpenTyCon tc -- open type family
357 | otherwise -- Newtype, datatype
358 = any exported_con (tyConDataCons tc)
359 -- Expose rep if any datacon or field is exported
361 || (isNewTyCon tc && isFFITy (snd (newTyConRep tc)))
362 -- Expose the rep for newtypes if the rep is an FFI type.
363 -- For a very annoying reason. 'Foreign import' is meant to
364 -- be able to look through newtypes transparently, but it
365 -- can only do that if it can "see" the newtype representation
367 exported_con con = any (`elemNameSet` exports)
368 (dataConName con : dataConFieldLabels con)
370 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
371 tidyInstances tidy_dfun ispecs
374 tidy ispec = setInstanceDFunId ispec $
375 tidy_dfun (instanceDFunId ispec)
377 getImplicitBinds :: TypeEnv -> [CoreBind]
378 getImplicitBinds type_env
379 = map get_defn (concatMap implicit_con_ids (typeEnvTyCons type_env)
380 ++ concatMap other_implicit_ids (typeEnvElts type_env))
381 -- Put the constructor wrappers first, because
382 -- other implicit bindings (notably the fromT functions arising
383 -- from generics) use the constructor wrappers. At least that's
384 -- what External Core likes
386 implicit_con_ids tc = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
388 other_implicit_ids (ATyCon tc) = filter (not . isNaughtyRecordSelector) (tyConSelIds tc)
389 -- The "naughty" ones are not real functions at all
390 -- They are there just so we can get decent error messages
391 -- See Note [Naughty record selectors] in MkId.lhs
392 other_implicit_ids (AClass cl) = classSelIds cl
393 other_implicit_ids other = []
395 get_defn :: Id -> CoreBind
396 get_defn id = NonRec id (tidyExpr emptyTidyEnv rhs)
398 rhs = unfoldingTemplate (idUnfolding id)
399 -- Don't forget to tidy the body ! Otherwise you get silly things like
400 -- \ tpl -> case tpl of tpl -> (tpl,tpl) -> tpl
404 %************************************************************************
406 \subsection{Step 1: finding externals}
408 %************************************************************************
411 findExternalIds :: Bool
413 -> IdEnv Bool -- In domain => external
414 -- Range = True <=> show unfolding
415 -- Step 1 from the notes above
416 findExternalIds omit_prags binds
418 = mkVarEnv [ (id,False) | id <- bindersOfBinds binds, isExportedId id ]
421 = foldr find emptyVarEnv binds
423 find (NonRec id rhs) needed
424 | need_id needed id = addExternal (id,rhs) needed
426 find (Rec prs) needed = find_prs prs needed
428 -- For a recursive group we have to look for a fixed point
430 | null needed_prs = needed
431 | otherwise = find_prs other_prs new_needed
433 (needed_prs, other_prs) = partition (need_pr needed) prs
434 new_needed = foldr addExternal needed needed_prs
436 -- The 'needed' set contains the Ids that are needed by earlier
437 -- interface file emissions. If the Id isn't in this set, and isn't
438 -- exported, there's no need to emit anything
439 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
440 need_pr needed_set (id,rhs) = need_id needed_set id
442 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
443 -- The Id is needed; extend the needed set
444 -- with it and its dependents (free vars etc)
445 addExternal (id,rhs) needed
446 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
449 add_occ id needed = extendVarEnv needed id False
450 -- "False" because we don't know we need the Id's unfolding
451 -- We'll override it later when we find the binding site
453 new_needed_ids = worker_ids `unionVarSet`
454 unfold_ids `unionVarSet`
458 dont_inline = isNeverActive (inlinePragInfo idinfo)
459 loop_breaker = isLoopBreaker (occInfo idinfo)
460 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
461 spec_ids = specInfoFreeVars (specInfo idinfo)
462 worker_info = workerInfo idinfo
464 -- Stuff to do with the Id's unfolding
465 -- The simplifier has put an up-to-date unfolding
466 -- in the IdInfo, but the RHS will do just as well
467 unfolding = unfoldingInfo idinfo
468 rhs_is_small = not (neverUnfold unfolding)
470 -- We leave the unfolding there even if there is a worker
471 -- In GHCI the unfolding is used by importers
472 -- When writing an interface file, we omit the unfolding
473 -- if there is a worker
474 show_unfold = not bottoming_fn && -- Not necessary
477 rhs_is_small -- Small enough
479 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
480 | otherwise = emptyVarSet
482 worker_ids = case worker_info of
483 HasWorker work_id _ -> unitVarSet work_id
484 otherwise -> emptyVarSet
489 findExternalRules :: [CoreBind]
490 -> [CoreRule] -- Non-local rules (i.e. ones for imported fns)
491 -> IdEnv a -- Ids that are exported, so we need their rules
493 -- The complete rules are gotten by combining
494 -- a) the non-local rules
495 -- b) rules embedded in the top-level Ids
496 findExternalRules binds non_local_rules ext_ids
497 = filter (not . internal_rule) (non_local_rules ++ local_rules)
500 | id <- bindersOfBinds binds,
501 id `elemVarEnv` ext_ids,
502 rule <- idCoreRules id
506 = any internal_id (varSetElems (ruleLhsFreeIds rule))
507 -- Don't export a rule whose LHS mentions a locally-defined
508 -- Id that is completely internal (i.e. not visible to an
511 internal_id id = not (id `elemVarEnv` ext_ids)
516 %************************************************************************
518 \subsection{Step 2: top-level tidying}
520 %************************************************************************
524 -- TopTidyEnv: when tidying we need to know
525 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
526 -- These may have arisen because the
527 -- renamer read in an interface file mentioning M.$wf, say,
528 -- and assigned it unique r77. If, on this compilation, we've
529 -- invented an Id whose name is $wf (but with a different unique)
530 -- we want to rename it to have unique r77, so that we can do easy
531 -- comparisons with stuff from the interface file
533 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
536 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
538 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 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 this_pkg = thisPackage (hsc_dflags hsc_env)
572 tidy env [] = return (env, [])
573 tidy env (b:bs) = do { (env1, b') <- tidyTopBind this_pkg mod nc_var ext_ids env b
574 ; (env2, bs') <- tidy env1 bs
575 ; return (env2, b':bs') }
577 ------------------------
578 tidyTopBind :: PackageId
580 -> IORef NameCache -- For allocating new unique names
581 -> IdEnv Bool -- Domain = Ids that should be external
582 -- True <=> their unfolding is external too
583 -> TidyEnv -> CoreBind
584 -> IO (TidyEnv, CoreBind)
586 tidyTopBind this_pkg mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (NonRec bndr rhs)
587 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
588 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
589 ; subst2 = extendVarEnv subst1 bndr bndr'
590 ; tidy_env2 = (occ_env2, subst2) }
591 ; return (tidy_env2, NonRec bndr' rhs') }
593 caf_info = hasCafRefs this_pkg subst1 (idArity bndr) rhs
595 tidyTopBind this_pkg mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (Rec prs)
596 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
597 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
599 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
600 ; tidy_env2 = (occ_env2, subst2) }
601 ; return (tidy_env2, Rec prs') }
605 -- the CafInfo for a recursive group says whether *any* rhs in
606 -- the group may refer indirectly to a CAF (because then, they all do).
608 | or [ mayHaveCafRefs (hasCafRefs this_pkg subst1 (idArity bndr) rhs)
609 | (bndr,rhs) <- prs ] = MayHaveCafRefs
610 | otherwise = NoCafRefs
612 --------------------------------------------------------------------
614 -- This is where we set names to local/global based on whether they really are
615 -- externally visible (see comment at the top of this module). If the name
616 -- was previously local, we have to give it a unique occurrence name if
617 -- we intend to externalise it.
618 tidyTopNames mod nc_var ext_ids occ_env [] = return (occ_env, [])
619 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
620 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
621 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
622 ; return (occ_env2, name:names) }
624 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
625 -> Id -> IO (TidyOccEnv, Name)
626 tidyTopName mod nc_var ext_ids occ_env id
627 | global && internal = return (occ_env, localiseName name)
629 | global && external = return (occ_env, name)
630 -- Global names are assumed to have been allocated by the renamer,
631 -- so they already have the "right" unique
632 -- And it's a system-wide unique too
634 -- Now we get to the real reason that all this is in the IO Monad:
635 -- we have to update the name cache in a nice atomic fashion
637 | local && internal = do { nc <- readIORef nc_var
638 ; let (nc', new_local_name) = mk_new_local nc
639 ; writeIORef nc_var nc'
640 ; return (occ_env', new_local_name) }
641 -- Even local, internal names must get a unique occurrence, because
642 -- if we do -split-objs we externalise the name later, in the code generator
644 -- Similarly, we must make sure it has a system-wide Unique, because
645 -- the byte-code generator builds a system-wide Name->BCO symbol table
647 | local && external = do { nc <- readIORef nc_var
648 ; let (nc', new_external_name) = mk_new_external nc
649 ; writeIORef nc_var nc'
650 ; return (occ_env', new_external_name) }
653 external = id `elemVarEnv` ext_ids
654 global = isExternalName name
656 internal = not external
657 mb_parent = nameParent_maybe name
658 loc = nameSrcLoc name
660 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
662 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
664 (us1, us2) = splitUniqSupply (nsUniqs nc)
665 uniq = uniqFromSupply us1
667 mk_new_external nc = allocateGlobalBinder nc mod occ' mb_parent loc
668 -- If we want to externalise a currently-local name, check
669 -- whether we have already assigned a unique for it.
670 -- If so, use it; if not, extend the table.
671 -- All this is done by allcoateGlobalBinder.
672 -- This is needed when *re*-compiling a module in GHCi; we must
673 -- use the same name for externally-visible things as we did before.
676 -----------------------------------------------------------
677 tidyTopPair :: VarEnv Bool
678 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
679 -- It is knot-tied: don't look at it!
682 -> (Id, CoreExpr) -- Binder and RHS before tidying
684 -- This function is the heart of Step 2
685 -- The rec_tidy_env is the one to use for the IdInfo
686 -- It's necessary because when we are dealing with a recursive
687 -- group, a variable late in the group might be mentioned
688 -- in the IdInfo of one early in the group
690 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
691 | isGlobalId bndr -- Injected binding for record selector, etc
692 = (bndr, tidyExpr rhs_tidy_env rhs)
696 bndr' = mkVanillaGlobal name' ty' idinfo'
697 ty' = tidyTopType (idType bndr)
698 rhs' = tidyExpr rhs_tidy_env rhs
699 idinfo' = tidyTopIdInfo rhs_tidy_env (isJust maybe_external)
700 (idInfo bndr) unfold_info arity
703 -- Expose an unfolding if ext_ids tells us to
704 -- Remember that ext_ids maps an Id to a Bool:
705 -- True to show the unfolding, False to hide it
706 maybe_external = lookupVarEnv ext_ids bndr
707 show_unfold = maybe_external `orElse` False
708 unfold_info | show_unfold = mkTopUnfolding rhs'
709 | otherwise = noUnfolding
711 -- Usually the Id will have an accurate arity on it, because
712 -- the simplifier has just run, but not always.
713 -- One case I found was when the last thing the simplifier
714 -- did was to let-bind a non-atomic argument and then float
715 -- it to the top level. So it seems more robust just to
717 arity = exprArity rhs
720 -- tidyTopIdInfo creates the final IdInfo for top-level
721 -- binders. There are two delicate pieces:
723 -- * Arity. After CoreTidy, this arity must not change any more.
724 -- Indeed, CorePrep must eta expand where necessary to make
725 -- the manifest arity equal to the claimed arity.
727 -- * CAF info. This must also remain valid through to code generation.
728 -- We add the info here so that it propagates to all
729 -- occurrences of the binders in RHSs, and hence to occurrences in
730 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
731 -- CoreToStg makes use of this when constructing SRTs.
733 tidyTopIdInfo tidy_env is_external idinfo unfold_info arity caf_info
734 | not is_external -- For internal Ids (not externally visible)
735 = vanillaIdInfo -- we only need enough info for code generation
736 -- Arity and strictness info are enough;
737 -- c.f. CoreTidy.tidyLetBndr
738 `setCafInfo` caf_info
740 `setAllStrictnessInfo` newStrictnessInfo idinfo
742 | otherwise -- Externally-visible Ids get the whole lot
744 `setCafInfo` caf_info
746 `setAllStrictnessInfo` newStrictnessInfo idinfo
747 `setInlinePragInfo` inlinePragInfo idinfo
748 `setUnfoldingInfo` unfold_info
749 `setWorkerInfo` tidyWorker tidy_env (workerInfo idinfo)
750 -- NB: we throw away the Rules
751 -- They have already been extracted by findExternalRules
755 ------------ Worker --------------
756 tidyWorker tidy_env (HasWorker work_id wrap_arity)
757 = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
758 tidyWorker tidy_env other
762 %************************************************************************
764 \subsection{Figuring out CafInfo for an expression}
766 %************************************************************************
768 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
769 We mark such things as `MayHaveCafRefs' because this information is
770 used to decide whether a particular closure needs to be referenced
773 There are two reasons for setting MayHaveCafRefs:
774 a) The RHS is a CAF: a top-level updatable thunk.
775 b) The RHS refers to something that MayHaveCafRefs
777 Possible improvement: In an effort to keep the number of CAFs (and
778 hence the size of the SRTs) down, we could also look at the expression and
779 decide whether it requires a small bounded amount of heap, so we can ignore
780 it as a CAF. In these cases however, we would need to use an additional
781 CAF list to keep track of non-collectable CAFs.
784 hasCafRefs :: PackageId -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
785 hasCafRefs this_pkg p arity expr
786 | is_caf || mentions_cafs = MayHaveCafRefs
787 | otherwise = NoCafRefs
789 mentions_cafs = isFastTrue (cafRefs p expr)
790 is_caf = not (arity > 0 || rhsIsStatic this_pkg expr)
791 -- NB. we pass in the arity of the expression, which is expected
792 -- to be calculated by exprArity. This is because exprArity
793 -- knows how much eta expansion is going to be done by
794 -- CorePrep later on, and we don't want to duplicate that
795 -- knowledge in rhsIsStatic below.
798 -- imported Ids first:
799 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
800 -- now Ids local to this module:
802 case lookupVarEnv p id of
803 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
804 Nothing -> fastBool False
806 cafRefs p (Lit l) = fastBool False
807 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
808 cafRefs p (Lam x e) = cafRefs p e
809 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
810 cafRefs p (Case e bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
811 cafRefs p (Note n e) = cafRefs p e
812 cafRefs p (Cast e co) = cafRefs p e
813 cafRefs p (Type t) = fastBool False
815 cafRefss p [] = fastBool False
816 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
818 -- hack for lazy-or over FastBool.
819 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))