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 )
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)
292 ; endPass dflags "Tidy Core" Opt_D_dump_simpl all_tidy_binds
293 ; dumpIfSet_core dflags Opt_D_dump_simpl
295 (pprRules tidy_rules)
297 ; return (CgGuts { cg_module = mod,
298 cg_tycons = alg_tycons,
299 cg_binds = all_tidy_binds,
300 cg_dir_imps = dir_imps,
301 cg_foreign = foreign_stubs,
302 cg_dep_pkgs = dep_pkgs deps,
303 cg_hpc_info = hpc_info },
305 ModDetails { md_types = tidy_type_env,
306 md_rules = tidy_rules,
307 md_insts = tidy_insts,
308 md_fam_insts = fam_insts,
309 md_exports = exports,
310 md_modBreaks = modBreaks,
311 md_vect_info = vect_info -- is already tidy
315 lookup_dfun type_env dfun_id
316 = case lookupTypeEnv type_env (idName dfun_id) of
317 Just (AnId dfun_id') -> dfun_id'
318 other -> pprPanic "lookup_dfun" (ppr dfun_id)
320 tidyTypeEnv :: Bool -> NameSet -> TypeEnv -> [CoreBind] -> TypeEnv
322 -- The competed type environment is gotten from
323 -- Dropping any wired-in things, and then
324 -- a) keeping the types and classes
325 -- b) removing all Ids,
326 -- c) adding Ids with correct IdInfo, including unfoldings,
327 -- gotten from the bindings
328 -- From (c) we keep only those Ids with External names;
329 -- the CoreTidy pass makes sure these are all and only
330 -- the externally-accessible ones
331 -- This truncates the type environment to include only the
332 -- exported Ids and things needed from them, which saves space
334 tidyTypeEnv omit_prags exports type_env tidy_binds
335 = let type_env1 = filterNameEnv keep_it type_env
336 type_env2 = extendTypeEnvWithIds type_env1 final_ids
337 type_env3 | omit_prags = mapNameEnv trim_thing type_env2
338 | otherwise = type_env2
342 final_ids = [ id | id <- bindersOfBinds tidy_binds,
343 isExternalName (idName id)]
345 -- We keep GlobalIds, because they won't appear
346 -- in the bindings from which final_ids are derived!
347 -- (The bindings bind LocalIds.)
348 keep_it thing | isWiredInThing thing = False
349 keep_it (AnId id) = isGlobalId id -- Keep GlobalIds (e.g. class ops)
350 keep_it other = True -- Keep all TyCons, DataCons, and Classes
354 ATyCon tc | mustExposeTyCon exports tc -> thing
355 | otherwise -> ATyCon (makeTyConAbstract tc)
357 AnId id | isImplicitId id -> thing
358 | otherwise -> AnId (id `setIdInfo` vanillaIdInfo)
362 mustExposeTyCon :: NameSet -- Exports
363 -> TyCon -- The tycon
364 -> Bool -- Can its rep be hidden?
365 -- We are compiling without -O, and thus trying to write as little as
366 -- possible into the interface file. But we must expose the details of
367 -- any data types whose constructors or fields are exported
368 mustExposeTyCon exports tc
369 | not (isAlgTyCon tc) -- Synonyms
371 | isEnumerationTyCon tc -- For an enumeration, exposing the constructors
372 = True -- won't lead to the need for further exposure
373 -- (This includes data types with no constructors.)
374 | isOpenTyCon tc -- open type family
376 | otherwise -- Newtype, datatype
377 = any exported_con (tyConDataCons tc)
378 -- Expose rep if any datacon or field is exported
380 || (isNewTyCon tc && isFFITy (snd (newTyConRep tc)))
381 -- Expose the rep for newtypes if the rep is an FFI type.
382 -- For a very annoying reason. 'Foreign import' is meant to
383 -- be able to look through newtypes transparently, but it
384 -- can only do that if it can "see" the newtype representation
386 exported_con con = any (`elemNameSet` exports)
387 (dataConName con : dataConFieldLabels con)
389 tidyInstances :: (DFunId -> DFunId) -> [Instance] -> [Instance]
390 tidyInstances tidy_dfun ispecs
393 tidy ispec = setInstanceDFunId ispec $
394 tidy_dfun (instanceDFunId ispec)
396 getImplicitBinds :: TypeEnv -> [CoreBind]
397 getImplicitBinds type_env
398 = map get_defn (concatMap implicit_con_ids (typeEnvTyCons type_env)
399 ++ concatMap other_implicit_ids (typeEnvElts type_env))
400 -- Put the constructor wrappers first, because
401 -- other implicit bindings (notably the fromT functions arising
402 -- from generics) use the constructor wrappers. At least that's
403 -- what External Core likes
405 implicit_con_ids tc = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
407 other_implicit_ids (ATyCon tc) = filter (not . isNaughtyRecordSelector) (tyConSelIds tc)
408 -- The "naughty" ones are not real functions at all
409 -- They are there just so we can get decent error messages
410 -- See Note [Naughty record selectors] in MkId.lhs
411 other_implicit_ids (AClass cl) = classSelIds cl
412 other_implicit_ids other = []
414 get_defn :: Id -> CoreBind
415 get_defn id = NonRec id (tidyExpr emptyTidyEnv rhs)
417 rhs = unfoldingTemplate (idUnfolding id)
418 -- Don't forget to tidy the body ! Otherwise you get silly things like
419 -- \ tpl -> case tpl of tpl -> (tpl,tpl) -> tpl
423 %************************************************************************
425 \subsection{Step 1: finding externals}
427 %************************************************************************
430 findExternalIds :: Bool
432 -> IdEnv Bool -- In domain => external
433 -- Range = True <=> show unfolding
434 -- Step 1 from the notes above
435 findExternalIds omit_prags binds
437 = mkVarEnv [ (id,False) | id <- bindersOfBinds binds, isExportedId id ]
440 = foldr find emptyVarEnv binds
442 find (NonRec id rhs) needed
443 | need_id needed id = addExternal (id,rhs) needed
445 find (Rec prs) needed = find_prs prs needed
447 -- For a recursive group we have to look for a fixed point
449 | null needed_prs = needed
450 | otherwise = find_prs other_prs new_needed
452 (needed_prs, other_prs) = partition (need_pr needed) prs
453 new_needed = foldr addExternal needed needed_prs
455 -- The 'needed' set contains the Ids that are needed by earlier
456 -- interface file emissions. If the Id isn't in this set, and isn't
457 -- exported, there's no need to emit anything
458 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
459 need_pr needed_set (id,rhs) = need_id needed_set id
461 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
462 -- The Id is needed; extend the needed set
463 -- with it and its dependents (free vars etc)
464 addExternal (id,rhs) needed
465 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
468 add_occ id needed | id `elemVarEnv` needed = needed
469 | otherwise = extendVarEnv needed id False
470 -- "False" because we don't know we need the Id's unfolding
471 -- Don't override existing bindings; we might have already set it to True
473 new_needed_ids = worker_ids `unionVarSet`
474 unfold_ids `unionVarSet`
478 dont_inline = isNeverActive (inlinePragInfo idinfo)
479 loop_breaker = isNonRuleLoopBreaker (occInfo idinfo)
480 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
481 spec_ids = specInfoFreeVars (specInfo idinfo)
482 worker_info = workerInfo idinfo
484 -- Stuff to do with the Id's unfolding
485 -- The simplifier has put an up-to-date unfolding
486 -- in the IdInfo, but the RHS will do just as well
487 unfolding = unfoldingInfo idinfo
488 rhs_is_small = not (neverUnfold unfolding)
490 -- We leave the unfolding there even if there is a worker
491 -- In GHCI the unfolding is used by importers
492 -- When writing an interface file, we omit the unfolding
493 -- if there is a worker
494 show_unfold = not bottoming_fn && -- Not necessary
497 rhs_is_small -- Small enough
499 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
500 | otherwise = emptyVarSet
502 worker_ids = case worker_info of
503 HasWorker work_id _ -> unitVarSet work_id
504 otherwise -> emptyVarSet
509 findExternalRules :: [CoreBind]
510 -> [CoreRule] -- Non-local rules (i.e. ones for imported fns)
511 -> IdEnv a -- Ids that are exported, so we need their rules
513 -- The complete rules are gotten by combining
514 -- a) the non-local rules
515 -- b) rules embedded in the top-level Ids
516 findExternalRules binds non_local_rules ext_ids
517 = filter (not . internal_rule) (non_local_rules ++ local_rules)
520 | id <- bindersOfBinds binds,
521 id `elemVarEnv` ext_ids,
522 rule <- idCoreRules id
526 = any internal_id (varSetElems (ruleLhsFreeIds rule))
527 -- Don't export a rule whose LHS mentions a locally-defined
528 -- Id that is completely internal (i.e. not visible to an
531 internal_id id = not (id `elemVarEnv` ext_ids)
536 %************************************************************************
538 \subsection{Step 2: top-level tidying}
540 %************************************************************************
544 -- TopTidyEnv: when tidying we need to know
545 -- * nc_var: The NameCache, containing a unique supply and any pre-ordained Names.
546 -- These may have arisen because the
547 -- renamer read in an interface file mentioning M.$wf, say,
548 -- and assigned it unique r77. If, on this compilation, we've
549 -- invented an Id whose name is $wf (but with a different unique)
550 -- we want to rename it to have unique r77, so that we can do easy
551 -- comparisons with stuff from the interface file
553 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
556 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
558 tidyTopBinds :: HscEnv
561 -> IdEnv Bool -- Domain = Ids that should be external
562 -- True <=> their unfolding is external too
564 -> IO (TidyEnv, [CoreBind])
566 tidyTopBinds hsc_env mod type_env ext_ids binds
567 = tidy init_env binds
569 nc_var = hsc_NC hsc_env
571 -- We also make sure to avoid any exported binders. Consider
572 -- f{-u1-} = 1 -- Local decl
574 -- f{-u2-} = 2 -- Exported decl
576 -- The second exported decl must 'get' the name 'f', so we
577 -- have to put 'f' in the avoids list before we get to the first
578 -- decl. tidyTopId then does a no-op on exported binders.
579 init_env = (initTidyOccEnv avoids, emptyVarEnv)
580 avoids = [getOccName name | bndr <- typeEnvIds type_env,
581 let name = idName bndr,
583 -- In computing our "avoids" list, we must include
585 -- all things with global names (assigned once and for
586 -- all by the renamer)
587 -- since their names are "taken".
588 -- The type environment is a convenient source of such things.
590 this_pkg = thisPackage (hsc_dflags hsc_env)
592 tidy env [] = return (env, [])
593 tidy env (b:bs) = do { (env1, b') <- tidyTopBind this_pkg mod nc_var ext_ids env b
594 ; (env2, bs') <- tidy env1 bs
595 ; return (env2, b':bs') }
597 ------------------------
598 tidyTopBind :: PackageId
600 -> IORef NameCache -- For allocating new unique names
601 -> IdEnv Bool -- Domain = Ids that should be external
602 -- True <=> their unfolding is external too
603 -> TidyEnv -> CoreBind
604 -> IO (TidyEnv, CoreBind)
606 tidyTopBind this_pkg mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (NonRec bndr rhs)
607 = do { (occ_env2, name') <- tidyTopName mod nc_var ext_ids occ_env1 bndr
608 ; let { (bndr', rhs') = tidyTopPair ext_ids tidy_env2 caf_info name' (bndr, rhs)
609 ; subst2 = extendVarEnv subst1 bndr bndr'
610 ; tidy_env2 = (occ_env2, subst2) }
611 ; return (tidy_env2, NonRec bndr' rhs') }
613 caf_info = hasCafRefs this_pkg subst1 (idArity bndr) rhs
615 tidyTopBind this_pkg mod nc_var ext_ids tidy_env1@(occ_env1,subst1) (Rec prs)
616 = do { (occ_env2, names') <- tidyTopNames mod nc_var ext_ids occ_env1 bndrs
617 ; let { prs' = zipWith (tidyTopPair ext_ids tidy_env2 caf_info)
619 ; subst2 = extendVarEnvList subst1 (bndrs `zip` map fst prs')
620 ; tidy_env2 = (occ_env2, subst2) }
621 ; return (tidy_env2, Rec prs') }
625 -- the CafInfo for a recursive group says whether *any* rhs in
626 -- the group may refer indirectly to a CAF (because then, they all do).
628 | or [ mayHaveCafRefs (hasCafRefs this_pkg subst1 (idArity bndr) rhs)
629 | (bndr,rhs) <- prs ] = MayHaveCafRefs
630 | otherwise = NoCafRefs
632 --------------------------------------------------------------------
634 -- This is where we set names to local/global based on whether they really are
635 -- externally visible (see comment at the top of this module). If the name
636 -- was previously local, we have to give it a unique occurrence name if
637 -- we intend to externalise it.
638 tidyTopNames mod nc_var ext_ids occ_env [] = return (occ_env, [])
639 tidyTopNames mod nc_var ext_ids occ_env (id:ids)
640 = do { (occ_env1, name) <- tidyTopName mod nc_var ext_ids occ_env id
641 ; (occ_env2, names) <- tidyTopNames mod nc_var ext_ids occ_env1 ids
642 ; return (occ_env2, name:names) }
644 tidyTopName :: Module -> IORef NameCache -> VarEnv Bool -> TidyOccEnv
645 -> Id -> IO (TidyOccEnv, Name)
646 tidyTopName mod nc_var ext_ids occ_env id
647 | global && internal = return (occ_env, localiseName name)
649 | global && external = return (occ_env, name)
650 -- Global names are assumed to have been allocated by the renamer,
651 -- so they already have the "right" unique
652 -- And it's a system-wide unique too
654 -- Now we get to the real reason that all this is in the IO Monad:
655 -- we have to update the name cache in a nice atomic fashion
657 | local && internal = do { nc <- readIORef nc_var
658 ; let (nc', new_local_name) = mk_new_local nc
659 ; writeIORef nc_var nc'
660 ; return (occ_env', new_local_name) }
661 -- Even local, internal names must get a unique occurrence, because
662 -- if we do -split-objs we externalise the name later, in the code generator
664 -- Similarly, we must make sure it has a system-wide Unique, because
665 -- the byte-code generator builds a system-wide Name->BCO symbol table
667 | local && external = do { nc <- readIORef nc_var
668 ; let (nc', new_external_name) = mk_new_external nc
669 ; writeIORef nc_var nc'
670 ; return (occ_env', new_external_name) }
673 external = id `elemVarEnv` ext_ids
674 global = isExternalName name
676 internal = not external
677 loc = nameSrcLoc name
679 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
681 mk_new_local nc = (nc { nsUniqs = us2 }, mkInternalName uniq occ' loc)
683 (us1, us2) = splitUniqSupply (nsUniqs nc)
684 uniq = uniqFromSupply us1
686 mk_new_external nc = allocateGlobalBinder nc mod occ' loc
687 -- If we want to externalise a currently-local name, check
688 -- whether we have already assigned a unique for it.
689 -- If so, use it; if not, extend the table.
690 -- All this is done by allcoateGlobalBinder.
691 -- This is needed when *re*-compiling a module in GHCi; we must
692 -- use the same name for externally-visible things as we did before.
695 -----------------------------------------------------------
696 tidyTopPair :: VarEnv Bool
697 -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
698 -- It is knot-tied: don't look at it!
701 -> (Id, CoreExpr) -- Binder and RHS before tidying
703 -- This function is the heart of Step 2
704 -- The rec_tidy_env is the one to use for the IdInfo
705 -- It's necessary because when we are dealing with a recursive
706 -- group, a variable late in the group might be mentioned
707 -- in the IdInfo of one early in the group
709 tidyTopPair ext_ids rhs_tidy_env caf_info name' (bndr, rhs)
710 | isGlobalId bndr -- Injected binding for record selector, etc
711 = (bndr, tidyExpr rhs_tidy_env rhs)
715 bndr' = mkVanillaGlobal name' ty' idinfo'
716 ty' = tidyTopType (idType bndr)
717 rhs' = tidyExpr rhs_tidy_env rhs
718 idinfo' = tidyTopIdInfo rhs_tidy_env (isJust maybe_external)
719 (idInfo bndr) unfold_info arity
722 -- Expose an unfolding if ext_ids tells us to
723 -- Remember that ext_ids maps an Id to a Bool:
724 -- True to show the unfolding, False to hide it
725 maybe_external = lookupVarEnv ext_ids bndr
726 show_unfold = maybe_external `orElse` False
727 unfold_info | show_unfold = mkTopUnfolding rhs'
728 | otherwise = noUnfolding
730 -- Usually the Id will have an accurate arity on it, because
731 -- the simplifier has just run, but not always.
732 -- One case I found was when the last thing the simplifier
733 -- did was to let-bind a non-atomic argument and then float
734 -- it to the top level. So it seems more robust just to
736 arity = exprArity rhs
739 -- tidyTopIdInfo creates the final IdInfo for top-level
740 -- binders. There are two delicate pieces:
742 -- * Arity. After CoreTidy, this arity must not change any more.
743 -- Indeed, CorePrep must eta expand where necessary to make
744 -- the manifest arity equal to the claimed arity.
746 -- * CAF info. This must also remain valid through to code generation.
747 -- We add the info here so that it propagates to all
748 -- occurrences of the binders in RHSs, and hence to occurrences in
749 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
750 -- CoreToStg makes use of this when constructing SRTs.
752 tidyTopIdInfo tidy_env is_external idinfo unfold_info arity caf_info
753 | not is_external -- For internal Ids (not externally visible)
754 = vanillaIdInfo -- we only need enough info for code generation
755 -- Arity and strictness info are enough;
756 -- c.f. CoreTidy.tidyLetBndr
757 `setCafInfo` caf_info
759 `setAllStrictnessInfo` newStrictnessInfo idinfo
761 | otherwise -- Externally-visible Ids get the whole lot
763 `setCafInfo` caf_info
765 `setAllStrictnessInfo` newStrictnessInfo idinfo
766 `setInlinePragInfo` inlinePragInfo idinfo
767 `setUnfoldingInfo` unfold_info
768 `setWorkerInfo` tidyWorker tidy_env (workerInfo idinfo)
769 -- NB: we throw away the Rules
770 -- They have already been extracted by findExternalRules
774 ------------ Worker --------------
775 tidyWorker tidy_env (HasWorker work_id wrap_arity)
776 = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
777 tidyWorker tidy_env other
781 %************************************************************************
783 \subsection{Figuring out CafInfo for an expression}
785 %************************************************************************
787 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
788 We mark such things as `MayHaveCafRefs' because this information is
789 used to decide whether a particular closure needs to be referenced
792 There are two reasons for setting MayHaveCafRefs:
793 a) The RHS is a CAF: a top-level updatable thunk.
794 b) The RHS refers to something that MayHaveCafRefs
796 Possible improvement: In an effort to keep the number of CAFs (and
797 hence the size of the SRTs) down, we could also look at the expression and
798 decide whether it requires a small bounded amount of heap, so we can ignore
799 it as a CAF. In these cases however, we would need to use an additional
800 CAF list to keep track of non-collectable CAFs.
803 hasCafRefs :: PackageId -> VarEnv Var -> Arity -> CoreExpr -> CafInfo
804 hasCafRefs this_pkg p arity expr
805 | is_caf || mentions_cafs
807 | otherwise = NoCafRefs
809 mentions_cafs = isFastTrue (cafRefs p expr)
810 is_caf = not (arity > 0 || rhsIsStatic this_pkg expr)
812 -- NB. we pass in the arity of the expression, which is expected
813 -- to be calculated by exprArity. This is because exprArity
814 -- knows how much eta expansion is going to be done by
815 -- CorePrep later on, and we don't want to duplicate that
816 -- knowledge in rhsIsStatic below.
819 -- imported Ids first:
820 | not (isLocalId id) = fastBool (mayHaveCafRefs (idCafInfo id))
821 -- now Ids local to this module:
823 case lookupVarEnv p id of
824 Just id' -> fastBool (mayHaveCafRefs (idCafInfo id'))
825 Nothing -> fastBool False
827 cafRefs p (Lit l) = fastBool False
828 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
829 cafRefs p (Lam x e) = cafRefs p e
830 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
831 cafRefs p (Case e bndr _ alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
832 cafRefs p (Note n e) = cafRefs p e
833 cafRefs p (Cast e co) = cafRefs p e
834 cafRefs p (Type t) = fastBool False
836 cafRefss p [] = fastBool False
837 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
839 -- hack for lazy-or over FastBool.
840 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))